Finally got me a 55 olds 2 door sedan, the 324 is locked up, want to put in a smb chev, is there a bell housing available so I can still use the original olds 3 speed manual?

 

Do all that you can to free the Olds up.
It is your choice, but no-o-o-o!!! on the SBC.

 

Ditto on trying to keep that 324. It's a cool engine, whereas except for 283/327, SBC are boring as hell. Even if you put faux Rocket valve covers on them.

Back in the day (here we go), the speed equipment companies made all sorts of stuff like that. Now, not so much.

If you're determined to go thru with the SBC swap, this might be a question better asked over on the H.A.M.B. http://www.jalopyjournal.com/forum/ because I'd almost bet money someone there has done this and can guide you thru the pitfalls (input shaft, clutch etc), and may even have the parts you need. Ya gotta remember that by 1955 a stick Oldsmobile was not at all common- they pushed HydraMatic.

 

Just as a point of reference...if you find a running 324 from an automatic, the standard transmission will bolt up - the hydramatics (Non-park, pre 56) used the same pilot as the standards. All you'd have to do would be swap the flywheel and the standard trans stuff...if you were closer I'd happily trade you a running 324 with a good auto for your non running with the 3 speed setup. It's your car, and it's your choice, but I would strongly recommend keeping it all Olds and without question keep that stick set up. Just my opinion.