I’m putting a 400 Pontiac from a 77 Trans AM into an 80 Trans AM and its proving to be hard.  The upper and lower motor mounts should be the same but nothing seems to fit and I must FORCE the mounts into place.   The upper mounts do not appear to be damaged and they exactly match the mounts from the 301 motor that came out of the 80 TA.  The lower mounts are new.

It really should not be this hard.  So here is the question - Do the lower mounts need to be relocated to a different position for this swap?   It looks like the frame is drilled for a location about a ½ inch higher and forward of the original mount location and it looks like things would fit a bit better if the lower mounts were relocated - but that will raise the front of the motor.  

The 301 block brackets and frame mounts should bolt in perfectly on the 77 400, at least they did on my 79 Formula. Any chance they have been altered? Did you pull the 301 yourself or did someone else have a different engine in there before you got it?
Steve  

I did pull the 301 myself and the upper and lower mounts look identical when comparing the 400 mounts to the ones from the 301. It appears that moving the lower mounts to a location forward of the 301 stock location will be necessary...  

I pulled my 301 and installed a 400 in my 1980 Trans Am with no motor mount problems the best I can remember. It was a wile back in 83 after I blew up the 301.