Manual trans swap info

many cranks were not machined for a pilot bushing, that would need to be done or replaced with one from a 4 speed or you could use a late model bearing that fits in the torque converter register that option may require shortening the input shaft of the transmission, you will also need to find a longer drive shaft when switching from a 727, a hole will need to be cut in the floor and a floor hump installed to make room for the shifter and shift rod, you will need a 130 tooth flywheel balanced for a 360, a bellhousing with the correct bearing opening to match the trans you are going to use, clutch/brake pedal assembly, Z-bar push rod clutch fork, and an A-body A-833 standard or overdrive transmission,
here are some links to help you out

http://www.slantsix.org/articles/4-speeds/ODA833fourspeed1.htm

http://www.darkside.ca/a-4spd.asp

http://www.brewersperformance.com/

http://www.passonperformance.com/