350 wont shift out of first...

[Axle]

Do you have a metal line to your vacuum modulator (just rubber line for connections)? If not, the vacuum will suck the line shut.

Vacuum connected to a manifold vacuum source? If connected to a carb make sure you are not on a ported line.

You can drive a th350 with the kickdown cable disconnected (its not a tv cable like an overdrive trans). When you disconnect the kickdown cable does it spring/pull back towards the trans? (too tight if it does).