Motor Mounts - Engine or Frame Specific?

Backstory:
We bought our 1985 F350 with a barely-hanging on 351W in it, and swapped it out with a 1992 351W while we built a new engine.

When we put the '92 351W in place, the motor mounts pushed against the oil pan to the point where it started leaking, so we did some cutting and grinding to relieve the pressure.

I'm guessing the issue is the size/shape of the pan.  The '85 had an external dip, the '92 had an internal dip.  But I don't know this for sure.

We're getting ready to drop in the engine that we built ('89 351W block, stroked to 393) and I want to replace the motor mounts.

Question:
Are the motor mounts specific to the engine block year, or the frame, or both (or neither!)?

Thanks!

(image of the interference, the oil pan sits "proud" of the block")

The motor mounts are different between the years, but I cannot tell you why that is.  I am a book dummy on this, all I know comes from a book etc.  

Did you use the 1985, 1989, or 1992 oil pan?  That may make a difference. Don't know.

If nobody else has a suggestion, I'd try buying both sets of motor mounts, one from 1985, and the other for 1989, then return the one you don't need.

Frame basic dimensions did not change from 1980-1997, but the perches (frame brackets) for the engines are engine family specific, and in some cases the cross member is different. First thing would be to check the VIN for what the original engine was. The perches may have a Ford engineering number which may help in identifying them. As far as I know, the 302 and 351 perches should be the same as the lower portion of the engines are basically identical.

Trucks use a "center" sump pan that has a well near the front the oil pump fits down into. I don't have a 351W to even take pictures of, I do have some good pictures of a 460 pan both off and on the engine.

the only "safe suggestion" that I would make is to order mounts for the year engine that is going in. now if they are considered interchangeable then you may find differences between brands. true that you do not want any unintended pressures leaning on any gasketed surfaces. they are leak points waiting for a reason as it is.