I have a 1991 Daytona with the 6G72 V6 and the A604 4-speed automatic transmission but from what I can tell the seals inside the transmission are shot and the car is stuck in limp mode.

I'm looking at swapping in a 5-speed manual if I can afford it but I have no clue which transmission would bolt onto the 6G72 properly or what else i need besides pedal assembly, shifter and cables.

Any info would be appreciated.

 

I have honestly never swapped one before, but usually the basics are the same on all cars:
Trans
Tranny mount, maybe 2 mounts depending on car
1 axle
Computer
Shifter assembly with cables and bushing
Clutch pedal, brake pedal, hardware, clutch cable
^If its hydro you need a master, slave, reservoir, and line
ECU
Reverse light wiring with switch
Flywheel, pressure plate, clutch, bearing, and bolts

I am sure I am missing a few things, but all in all its not worth the time unless you have a donor car. Your better off fixing it to sell then buy a 5 speed car.