A500 in an Early A

I might have to change plans to go from my 833 to an automatic in my early A. I gotta use what I have on hand - a rebuilt A500. I know just find a 904 (not cost effective). I know the A500’s require some floorpan and crossmember surgery in the later A’s. For the early A I’m guessing the crossmember will probably be heavily modified. A search revealed nothing where it’s been done in an early A. If anyone can point me to where it’s been done, thanks in advance.