You'll want an '85 or later transmission, the early ones have weak pumps. For the rearend gear, that will partialy depend on overall usage plans and also tire size. Having said that, I have an S10 with a 700R4, 235/75/15 tires and a 4.10 rear gear, it works very well. Without knowing what year truck, engine size, tire size, and what rearend is in it (stock, later truck, Camaro, etc) It's somewhat difficult to give an exact gear ratio, as it can vary on availablity for a given differential. I can say that 3.73-4.11 would be a good range, though. Might even be able to go with a 3.42 if you have enough engine to pull it.
