As crenwelge says basically nothing swaps between the early and late transmissions. Including the bellhousings.
If you have a '55 bellhousing with that replacement motor, you will need to modify the mounts to use that bellhousing. If you have a '49 bellhousing, it should bolt up where the '47 came out. I think.
When you change to the later bellhousing you will need to modify the clutch linkage and I can't help you there, I know people have done it, but I'm not one of them. Send a PM to rustednuts and ask him to read this thread. He converted an early GMC COE to use the SM420 and might be able to expand or correct what I've said.
The '49 4-speed is an SM420. They became the standard 4-speed in '48 and were used into the 60's. The transmission was used in both open and closed driveline configurations and you should be able to simply swap the pieces to convert from one to the other.
These transmissions aren't that hard to come by, you can probably find an open driveline type SM420 as easily as the parts to convert the one you have. If you can locate MotherTrucker he is in Arizona and probably has the parts you need. Check OldGMCGTrucks.com to find him.
