I'd like to start w/Semper Fi! The other thing would be a trans adapter. If you don't wanna run the stock tranny, you are either gonna need to do some deep research into vintage trans adapters, or find a good friend that builds them. Not gonna be a cheap switch though. The last place that I knew of that made the trans adapters for early Rockets stopped making them due to all the subtle changes between years and models. Good luck.
there are at least three manufactures currently making adapters to put modern transmissions behind the early Olds motors. there were several manufactures making them back in the day, they would either be a bell or plate the stock setup is limited to puting the '50 Olds/Cad Lasalle transmissions, or the next generation Olds selector transmissions behind them. what transmission you use is up to you. what is the rest of the package? a light car with a souped motor and floor shift, or heavy cruiser with column shift or....?
I'm not 100% positive quite yet. My ideal plan would be build a roadster or coupe but we'll see how that plan unfolds. I found a great deal on a good engine and I dont want to pass it up and regret it later.
that sounds like a good plan to me here's another great thread http://www.jalopyjournal.com/forum/showthread.php?t=47584
I think I'd stick with an early 4 speed Hydra-Matic , which will, of course, bolt to your Olds 303. They're strong transmissions, and were much respected in the early days of gasser drag cars. In fact, when I think of the 60s AG/S cars like Stone, Woods & Cook, I can still hear that Hydra-Matic going through the gears ! Yeah, I know...street rods are supposed to have stick shift , but I think this is a legitimate exception. And, through second gear up to about 45 mph, the Hydra-Matic car will pull a stick shift car. ( I beat a lot of mighty machines in my '55 Olds, up to 45 mph anyway.) Things calm down a bit, however, when it hits third gear.
This is one of my big questions for the future too, options are pretty clear its either a stock Hydro set up, a cad/lasalle deal or an adaptor and on to one of the more modern GM 4-5 speeds, all the stuff is pretty readlly avail around the place for any of those options.