fuel tanks

Probably been flogged to death...but here goes. Project is to R+R sending/draw units, and fill/vent tubes in both tanks...front tank only has 5 gallons of usable fuel (showerhead assembly broken, fuel gauge non-op), rear works ok, but is original, so it gets replaced also. Here's the problem...when sourcing parts, I find that the tank opening for the sending/draw units are 2 inches on the original tanks, but cannot source original/replacement units for the sending/draw units. The available replacements only work in a 3.5 inch opening, which is the opening on tanks from '85 on.. My question is this: Will the front midship 19 gallon tank listed for a 1985 work on my '84? And will I have issues with the fill/vent tube assemblies? Same question for the rear 19 gallon tank.

I'm pretty sure that the tanks with the larger openings go right in where the earlier tanks were.  The only issue you should have is getting the right sending unit.  But, Ford did make a number of trucks in '85 and '6 that still had mechanical pumps, so there are sending units for them w/o the electric, in-tank pump.

Both the 300 six and the 351HO are in this category as they didn't have an electric pump in those years.  But the 460 is a different story as it came both ways - with a mechanical pump or with in-tank pumps.

And, I think the filler tubes stayed the same.  But you can check that out in the snippet below from the page at: Documentation/Fuel Systems/Fuel System Part #'s/Fuel Filler Pipes.  (Man, that's complex!  )

However, lets see what others have to say.  Maybe I missed something?

Good info...and those fill tubes for '84s are impossible to find. Probably wind up fixing whats there, hopefully, all it needs is repairing/replacing the vent tube...can only trickle fuel in at present. So, I think I'll pull the bed and see if that front sending unit can be repaired...and see about fixing the fill tubes. Just wish the folks that are selling those sendingdraw unbits would specify whether they are for gas, diesel or both. Cannot go by whether they have one or two inlet/outlet lines...

If the issue is the speed of fill then you need to switch to the later style filler tube.  The Bullnose fillers run gas down the outside and vent air back up the little hose in the middle.  But the later ones put the gas down the middle and air up the outside.  They are said to be much better though I have yet to change over.

Others have, so maybe they'll be along to comment.

They are greatly improved. If you use the 3.5" opening the older sender/pickup/pump assembly will go in, but the alignment tabs are in the wrong place. The older tanks have a ring to keep the inner vent tube in place, the later tanks lack this due to the change in the fillers.

Not sure on what you are saying...I'm diesel...no pump needed. The sending/draw unit tank hole is 2 inches in the original configuration...changed to 3,5 in 1985, so I'll have to replace the tank if I want a new sending/draw unit. Both use lock rings. So long as the fill tube size, vent system and attachment is the same on the '84 and '85 tanks, I'll have no problem. Not going to be using high speed pumps, so the faster newer systems are not something I'll really need. Unless I've misconstrued everything I've read on this and other forums....LOL!!!! Then I'm in trouble...

The "faster, newer," fill tubes are worlds better.
It's up to you.

If you chose to upgrade tanks, then you will have a consistent system
.

Here's the latest...Pulled the bed, r+r'd the fill tubes/vent tubes, added a length of hose to the draw unit so it would reach to the bottom of the tank...sucked up debris, and now switch valve is stuck, cannot switch to the rear tank. At this point, I'd like to confirm that a midship 19 gallon tank for a 1985 F250 is compatible with a 1984 F250...with the exception of the hole for the sending/draw unit, which is 3.5 inches in '85, vs 2 inch i '84, and that the fill tube vent design is the same, ie using a small inner tube to vent the air when filling. Original sending/draw unit is suspect...thinking I want to replace it with new...but 2 inch units are not available, so go with a 1985 tank with the 3.5 inch hole for the send/draw unit so I can buy a new sending unit. Tired of screwing around with it...want to replace tank, sending unit, and switch valve and be done with it, witghout getting halfway thru the project and finding out that "oh gee...this doesn't fit.."...and having to wait 6 weeks for the correct part to arrive, or worse, have to start from scratch. Thx for the replies!!! Hope to solve this...else it's going  straight to the car crusher...

Like Gary's page shows, same same '80-'86.

The fill portion was concentric to the vent tube up until 1987, when Ford wised up and sent the fuel down the middle.

The '85/'86 tanks fit right into the bricknose trucks as well.
But the '87/ senders read backwards and have at least twice the resistance.

You're fine using a '85/'86 tank and sender in your IDI.

question is can you reuse your old hose if you go with the late model filler neck.

I thought of doing that but flare sides are impossible nearly to find the filler neck hose itself from the neck to the tank.

Then again I am not sure if the 85/86 fuel tank I am getting for my fuel injection setup would be capable of accepting the later style filler neck tube.

As far as was mentioned earlier the hoses/necks should be the same, we installed a later tank in a '82 F150 at work for a 5.0 coyote swap and the OE filler hose still connected just fine.

While you guys were talking about sending units, I found this place several years ago. Have never used them but Might have to by the time I get around to all my projects.
http://tristarrradiator.com/
They will rebuild your sending unit to new condition. Take a look at some of the before and after pictures.

Rusty,

If you use a '87/ fill hose you need the '87/ fill neck.
These sit a little different angle behind the box.

If you want details on Flaresides you should ask Dave.
He set his truck up with dual tanks.

But this gentleman wants to use an '85-'86 large bung tank in his diesel Styleside.
And for that, it's no problem using a '80-'84 fill hose.