500 caddy questions

well im off to the farm tomorrow with my 73 eldorado to tear the motor out of it for my t bucket.
i have a question for anyone who may know. i believe i have to use the converter out of the fwd automatic to be able to bolt a std olds 400 tranny to it.
WHY? isnt the tansaxle the same that is in a fwd olds rivy that was bolted to a 455 olds , or is the ringear in a rivy different for the coverter from the fwd tranny.
just thinkin ahead but i am goig to match up bolt holes before i even start.
i know i put a used 400 tranny behind a 454 chev once and none of the flywheel to coverter holes lined up never knew why . had to drill the flex plate with new lined up holes worked ok too.

I am also a Caddy fan. I'm stuffing mine in a 49 Ford truck. There is nothing better thatn big cubes and tons of torque.
Yes, the Eldo has the same transaxle as the rivvy and the toro. Its a TH425 I think. As far as I know the flexplates for all of the Caddilac trannys were all the same for those years, frt wheel drive or rear wheel drive. I think the Olds flexplates carry a different part # but I don't know how much different they are. A local parts store might be able to help you out with it.

Good luck on the T bucket, it sounds like a fun ride

hey bobby t thanks for the input , got the motor out and already into the bucket . made motor mounts today and tranny mount. i bolted the bop 400 tranny up to the caddy engine and the convertor holes match but it seems that it still wont fit it, the convertor does not seem to want to pull ahead to the flexplate. didnt spend much time on it but i kept the caddy convertor and will split it to see if the little snout on the convertor is the same size or not.
next step getting the driveshaft shortened something i know i cant do myself

i can tell your right now why it doesn't want to go in.... nose on the converter is probably too long and so its hitting the crank, pretty common problem with mixing converters, probably the best way would be to get ahold of someone that makes converters and have a custom high stall speed converter made for you... it'll be more fun than a stock converter any ways

that would make sense as the convertor thats in the tranny right now came from a olds 455 and it wont pull in. i am going to pull the tranny and compare the original convertor from the caddy to the olds convertor and see whats up.
i dont know if i want to go to a higher stall convertor as the car is pretty light and with the 500 caddy traction will be a problem no matter if stock convertor or not.
something to think about though, thanks!!