Ok here's my problem. I bought a 73 k10 and the guy threw in a th350 that "works" cause the one in the truck didnt. so this weekend i did the swap and now when I go to drive it. it doesnt want to shift out of 1st there are a couple of options i know of but i would like to know if its something simple before I get drastic with it.

 

I had the same problem. Tranny wouldn't shift out of low gear. My problem was simple. Broken vacuum line to the transmission.