Wiring for EFI installation

At this point the engine bay in my 84 is completely empty and I'm getting the wiring harness setup for my Edelbrock Pro-Flo 4. Obviously the carbed 351W is out. What is very interesting is how much EFI stuff is in there, even though the truck didn't have EFI. It has an EEC under the dash and wiring and connectors running through a single large firewall grommet for TAD, TAB, a Dithering Selenoid (WTFIT?) as well as the MAP, TPS, VIP Tester and other non EFI stuff. I'm assuming that the harness was shared with the EFI 5.0 in 84 and unused connections just hung? I'm not sure; the PO cut out the EGR so it's hard to tell what this rats nest of wires and connections looked like from the factory..

After going through some of the existing wiring I'm probably going to replace the cluster and gauges with a New Vintage USA unit. Supposedly the Phoenix Direct Drive unit is pretty much plug and play with stock and aftermarket wiring.

If I'm installing an aftermarket EFI and new gauges, can I ditch the entire stock EEC? I noticed the vacuum speed control system and wiring runs off a different section of the harness and different "brain". Would that still work without the EEC? Would I have to wire in the TPS from the Pro-Flo for the cruise to keep working?

Many of the non-EFI systems still had TAD, TAB, etc.  They got pretty complex.

But yes, if you are going with an aftermarket EFI system you can, and should, remove the EEC and associated wiring.

And the speed control is completely separate.  It needs nothing from any other system.  Just the transducer input from the speedo to tell it how fast it is going, and vacuum from the engine that it uses to move the servo to pull the throttle open.  It has an electronics box under the dash left of the ash tray.