Help make my mind up: Trans Swap/Rebuild

[SayBye]

Finally found some motivation to get going on my inline 6 64 again yesterday, took it for a spin around some back roads and man did it feel good!

My 3 speed goes into first and third fine and will hold position, however when shifted into 2nd gear itll hold til about 2500 rpm then pop or jump out of gear.

So at this point Im pondering on whats gonna be the best bang for my buck and what im gonna be happier with in the long run. My column shift is basically worn slap out, so more than likely if I do do the rebuild, Ill be looking at going to a floor setup. With that said, Im not opposed to going with an automatic, and honestly might be happier with it in the long run.

This is a rusty patina truck, some of yall have seen my project thread a while back. Whats gonna be my cheapest option? I heard these 3 speeds weren't very expensive to rebuild. But a used automatic might be around the same price? What automatic will bolt right into these trucks?

What automatic trans will bolt right in to these I6's?