1981 1ton th400 np205 sbc: my problem is the truck ran fine when it was parked, went to go move it and nothing, no 1st, 2nd, drive, or reverse. the fluid is full, not burnt, tcase engaged. I need a spot to start, govoner? vaccume modulator? any help would be great thanks.

Things I would check

1) Fluid level
2) Shift linkage
3) Line pressure

thanks for the advice: so how do I check line pressure and what should it be?