I am about to install a TH350 tranny in my 89 Firebird to replace my crappy *** 700R4, but what kind of torque converter should I use and what is the difference between a lock up and non lockup?? which is best for a 89 Firebird with a 305 TBI? Is there a particular rpm range that is best if I go with a lockup b/c a lockup converter is what everyone is saying I should get, but I didn't know why?
Also, what is the governor's actual purpose on the cars and are they necessary? Can they be disabled? Because the 350 Trans Ams and GTAs don't got a governor.

 

You should get a non-lockup converter, because that's what the 350 uses.

All automatic transmissions up until the electronically-shifted ones have a governor, including the ones in 350 cars. That's the thing that tells the transmission how fast the car is going, which is one of the key factors in how it knows when to be in what gear.

 

It would depend on which TH350 you have, a 350C (MV4) or 350 (M38). The 350C is designed to use a lockup converter. I think you are confusing the top speed governor in the ECM on some F bodies with the governor in the transmission, two different things.