Overdrive tranny in an A-body

It's understandable that people are going to worry; when we're talking about jacking up a heavy object underneath your car; hoping it doesn't have to come back down out of there immediately. The 500 and the 518 have the same overdrive, so cutting out the rear bracing is a given on both. And on a 67 and later, that's the only mod; outside of the bolt in crossmember. The only difference between the 500 and 518 installation is on the pre 67 A's only; where the 500 fits just like the 67 ups, but the 518 has a bigger bulkier bell housing that requires mods on both sides of the car; (Same as a 727). It's the area to the right of your toes when your foot is on the gas; and the corresponding area on the passenger side. The pre 67 has these two 3" diameter bumps sticking down.