Went to put the TH400 in my car, and for whatever reason it didn't occur to me that the mounting pad would be wider on a 400 than the 700R. So I went to autozone to get a new mount, have to order it, bring it home aaaanddd...it's the same width at the 700R mount...

So this mount had more material and looked beefier than the 700R mount that came from the factory so I egged out the holes and got it to fit (using large washers on the bolt to provide some support). But I'm pretty sure this is a terrible idea, because I can see the car going to shift and just tearing the maybe 1/8" of material left on each side.

So long story short, am I correct in assuming this is a bad idea and nothing more than a temporary fix, and what part number do I need that will have two tranny mount holes and one X-member hole? Or, can I weld in the washers that I put on the bolt and assume that this will work for me?

 

Best thing to do is, instead of using the 100% IRONCLAD CERTAIN TAKE-IT-TO-THE-BANK ABSOLUTELY POSITIVELY GUARANTEED TO BREAK IN HALF 1-stud-down crap, get the old 2-bolt-up mount for 350 & 400, choosing carefully to find one that the 2 metal halves captivate each other when the spooge breaks as it ALWAYS does, and add the 2 slots to your crossmember.

 

If you removed your torque arm from the trans., you removed most of the concern. Trans mounts have way more issues on a torque-arm F-body than cars that lack the torque arm.

Lock-washer and / or loc-tite your bolts, torque them properly, and check them when you change your oil. The 1/8" of material outside the bolt hole isn't the issue. The steel plate on both sides of it should hold fine if the bolts are torqued right.