Not sure what to do with the transmission in the 79 z28.
The 3 speed is killing me on the highway and I'm sure it has the 373's in it. Should I stick with the the th350 and do gears or swap to a 700r4 or 4 speed?

Can I have a different 3rd put into the th350? WHats the most cose effective thing to do? I really dont want a stick, have the 6 speed in the 99 and I like not having to shift this one

Swap in a 700r4. The 3.73's will love the new trans. http://nastyz28.com

I would go with either a 200 or a 700 R4. The OD is what you are needing.

Going to a 4 speed would be the same as the Turbo 350. The final gear ratio fron both transmissions is 1 to 1. Only gain in a four speed is possibly a lower first gear ratio.

700r4 but make sure the tv cable is adjusted properly or KABOOM goes your tranny clutches