stuffing a 71-75 olds or buick 455 into a 84 Lesabre 2dr

[84lesabre2dr]

im trying to shoehorn a 455 into my lesabre, and im pretty sure it will fit but im having transmission issues.some older mechanics tell me that the tail housing of a turbo 400 or 350bolted to the 455 wouldnt bolt into the stock crossmember. The car was originally equiped with a tiny 307 and turbo 200 tranny. any hints on how to make it fit?

[MagicRat]

I think the 307 mounts should fit the 455, but the 455 will turn the 200 trans into corn flakes, eventually. Consider the following project that I did, if you need an alternative route:

I put an Olds 455 into an '81 CadillacFleetwood which was the same basic chassis as yours.

Get a cross member from a '77 - 81 Caddy, it will fit your frame and will bolt up to a THM 400.
Get a 400 trans with the Buick - olds -Cadillac bolt pattern.

With my Caddy, I installed the cross member, then slipped the engine and 400 trans (bolted together) into the car. I had the original 455 engine mounts bolted to the block.

I aligned the trans into the perfect spot; then aligned the engine so it sat straight.
Pay attention to the driveline angularity. The angle, or tilt of the trans output shaft must match the angle of the differential pinion shaft, and must be perfectly in line, or else you will have a driveline vibration. You can do the alignment by shimming or grinding at the engien mounts as required. For my car, the stock 455 mounts were almost perfect and needed minimal work.

Then weld the mounts to the frame at the engine cradle, and the installlation is done.

The plumbing and electrical are pretty straightforward, the 307 hoses should line up, and some basic wiring fabrication will be needed for the ignition.