By 1970, I believe all the Chevy engines had Quadrajet carbs, so you've got an earlier-model intake on yours. If the port at the back of the carb is 1/4" pipe thread or larger, you can put in a 1/4 NPT to 3/8" tubing fitting and run the PCV hose to it, which just happens to be 3/8" inside diameter- - - -handy, huh? I'd suggest putting a PCV grommet into the passenger's side valve cover in place of one of the filler caps, but be sure there's a baffle inside the valve cover to prevent the PCV valve from sucking in liquid oil.
Does the 4GC have a "dashpot" installed on the throttle linkage? It's a spring-loaded throttle stop that returns the linkage to idle gradually, rather than letting it close suddenly. Every 4GC I've ever worked on has one, and some of them have a vacuum connection to assist in the throttle-closing process. If the vacuum is low, like after a sudden acceleration, the dashpot drops the throttle linkage back slower, to prevent the stall you're describing. Other dashpots simply have a spring and a diaphragm, which acts like a shock absorber for the throttle linkage.
Jerry
