Yes, but you would probably wind up with a better product if you kept the TM GB and just upgraded it.
I put the following parts in my stock TM gearbox:
Guarder SP120 spring
Guarder standard gears
Guarder steel bearing spring guide
Guarder cut off lever
G&P polyacetate piston (white)
G&P piston head (non bearing)
Systema piston head O ring
DeepFire bushings
I have 36,000 rounds through the gun. The stock TM EG700 motor burned out after 20,000 rounds, I replaced it with a G&P M120 motor.
The gun shoots 425fps w/ .20g BB @ 23bps with a Sanyo 9.6v NiCad battery.
My upgraded/custom TM AK47: