The Stovebolt Site Forums The Shop Area Engine Shop 3 speed tranny question for my 1966 283

I own a 283 that according to the engine castings came out of a 1966 C-10 or C-20 with a manual transmission and a two barrel carb. I am looking to marry it to a GM 3-speed tranny that will have the floor shift. I am looking to put this in my 1956 3100 that currently has another 283 with a 4 speed granny low "box" type tranny currently ( I was told this current 283 is from a 67 bel-air but am not sure and haven't checked the numbers since they're hard to see currently in the truck and covered with grease and grime. The current 283 in the 56 needs to be overhauled and the 1966 283 has been overhauled, so should be a big improvement over the existing one that needs overhauled in a major way. My question is this, how hard will it be to source a bell housing to marry the two together and where is a good place to source one? Any watch outs with getting the 3 speed into the 56? I believe the tranny is coming with all the necessary linkages for a floor shift, but if anything is missing, how big an issue is that? Any issues with getting the drive shaft to match-up or find a different one to make it work? I don't consider myself a mechanic, but have quite a few friends that will be able to help me out. I originally was going to put a muncie 4-speed in the truck, but the cost was just too much for me. And this 3 speed i'm looking at is in good condition and coming from a trusted source who is basically giving it to me. Again, thanks for any words of advise.
PS: I believe the rear-end in the 56 3100 is the original rear-end. Any issues with this change up in regards to the rear-end? Would there be a better one to put in there to match up? This new engine will have a 4 barrel and i assume much more power than this other one.

what are you hoping to gain by going to the 3 speed over the current 4 speed that is in it? (sounds like your existing tranny is the sm420). Is there anything wrong with the existing tranny?

Just bolt the new engine in and drive. You've got a "3 speed" already- - - -just don't use granny as a traffic gear. The advantage over the the 3 speed is a synchronized 2nd. in the SM 420 that can be engaged without coming to a full stop, something most 3 speeds don't have. The exception is the full-synchro Saginaw 3 speed. If the side cover on the 3 speed you're considering has four bolts it doesn't have a synchronized 1st. gear. Saginaw transmissions have 7-bolt side covers. High gear in the SM-420 and both 3 speeds is still 1:1, so there's no cruise RPM advantage.
Jerry

The 66 engine will bolt right up to the 56 bell housing. The 3 speed trans will bolt right up to the bell housing that the 4 speed was. I agree you are better off with original trans. unless you get a T-5 o-drive trans. It will bolt up to the same bell housing with some simple mods to the trans.
George

You will need to modify the driveshaft to change from the SM420 to a 3 speed. Also some of the 3 speed floor shift conversions mount on the rear of the transmission and and don't offer much clearance with the seat. If you are looking for better highway speeds, put an overdrive in it.
Fred