Problems with transmission in 4wd chevy pickup 1974

I have a 1975 Chevy pickup that does fine till I get to low speeds then you have to really rev it to keep it from stalling. The transfer case is still on the vehicle but long ago disconnected and the front differ replaced with a wishbone type suspension. I’m wondering if the torque converter is locked up of perhaps this has something to do with the transfer case.

How can one “rev” a motor that’s in gear? If your converter (somehow) was involved, I would think that you would find it impossible to idle in gear. I would tend to look toward the t-case (as you speculated). I can’t construct the scenario that would make it a factor, but that’s where I would look. Do you have it in a given range? (AWD, 4HI, 4L, etc.). Have you explored what happens when you change the range …or is the selector removed?

Well, I press on the gas peddle and it raises the engine RPM’s so that’s how I rev the engine.
That keeps it from stalling out on me seems to force the torque converter to let go but it also spins the back tires usually. The selector on the transfer case is long gone.