The Stovebolt Site Forums The Shop Area Driveline SM318 tail shaft removal and install, seal and bushing

You will need to disassemble the transmission to get it back together. You now have all the needle bearings in the bottom of the case.
To replace the rear bushing, expand the snap ring behind second gear and drive the mainshaft out. You can now remove the seal and drive the bushing out with a punch or chisel at the slot in the tail housing.
The seal is common to just about all Chevy manual transmissions, PG and TH350 at any parts store.
The seal number from my source, Anahiem Gear, in Anaheim CA is 8850, the bushing is 8008.
I don't know if those part numbers will help you in your area however.

To reassemble: Remove the side cover & clutch gear. There are two rows of needle bearings inside of the clutch gear.
Using grease to keep the needle bearings in place, install the larger needles in the bottom position, then install washer A
Next install washer B with the shinny side out and install the smaller needle bearings up against the washer

At this point you may also need a gasket set. It will be necessary to line up the syncro with the main shaft and the clutch gear when re-assembling the components.

Fred