This is going to sound strange, but I need someone to help me out here. These differences are going to be crucial to my current project.

My car is an '85 GSL-SE. Which, to my knowledge should have the 13B engine in it, and whose motor mounts are different from the 12A.

Now, I bought my car without the motor, but the mounts that are sitting in it now look like the base model mounts. Not like the 13B mounts.

How do I determine if the crossmember is for a 13B engine, or for a 12A car?

The crossmembers of12A and 13B cars have mount locations ~3/4" apart.

The picture on the left is for the 13B cars, the simple one on the right is for 12A cars.

My '85 GSL-SE has the mounts on the right.

How can I determine what crossmember my car has in it?

 

the 12A and the 13B use the same exact engine mounts. they are pictured in the pic on the right. the other square mount was not used until 1986 when all 7's went to the 13B. completely different front cover than the 13B from 84-85.

the crossmember that mounts to the front of the engine on the 12A and 13B are identical. the GSL-SE with the 13B for 84-85 had the mounts for the engine mounts welded farther forward on the engine cradle vs. the 12A powered 7's. this accomidated for the extra length of the 13B.

 

There is a slight difference in the SE mounts. The LH mount is the same for either engine, the 12A and manual 13B have the same RH mount, the 13B auto takes a different mount. Have no clue why there is a difference. I believe the RH mount is slightly taller than the LH and sometimes has a a dot of white paint on the mount to differentiate between the 2.

The Black Dragon catalog shows the different part #s for the mounts, yet lists the same part # for the front cross member engine mount.

 

hmmm...that's interesting. Pretty much every single parts place (Napa, O'Reilly, Autozone, Pep Boys, even Rock Auto) show the mount on the left for the GSL-SE 1st gen. It had me pretty confused. Thanks for the clarification!!!

So basically the actual cradle for the two engines in the 1st gen are the same, except that the mount points (holes that the rubber mounts bolt into) are ~3/4" forward for the 13b compared to the 12.

Theoretically, if I wanted to put a 12a into my car, I would drill holes ~3/4" rear-ward from where they are now.

 

The front engine mount is the same, it's the engine cradle that's different between the 12A/13B. Most just simply slot the front mount when swapping from one engine to the other.