Hard pedal/ no trans kick down
 

So just picked up a near dead 84 k5 with 400 sbc 700r4 and np208 tcase.

My gas pedal is real stiff and when I get on it it acts like it wants to downshift theen shifts back up almost like the trans is slipping a little but the trans is brand new. Maybe 1000 miles on it. But here's some back story info.

My buddy had it before me and thought it had a rock knockk so he pulled the engine but didn't disconnect the kick down cable so it yanked pretty hard on the cable, he ended up putting the 400 back in after looking at it and realizing it wasn't an internal knoc, but it sat for about a year getting started up maybe once every couple months, before he pulled the motor it ran great pedal felt normal it just needed a little love.

So I bought it from him put a new 44.5" kickdown cable on it and we've adjusted it a few times and the pedal got soft, but it wasn't kicking down at all, so adjusted it again now it feels like it wants to kick down but its still real stiff and takes everything I got to floor it and doesn't feel even close to as responsive as my old 79 k10 with a 400. So I'm kind of stumpedd.

I bought a new fuel pump/push rod for it to solve the knock I believe, also have a cam, whole new valve train, and new timing kit with chain. Also picked up a few new seals and trans pan gasket/filter kit for it. Just haven't gotten around to getting em put in yet, so figured I'd reach out to some more knowledgeable folks on these old pickups and see what y'all recommended. Thanks