1990 Pontiac Firebird

I need a little more detail about what you mean "No power on the dash."

Are you saying there's no power with the instrument cluster, the ignition key doesn't work, the radio doesn't work, etc? And what about the rest of the interior?

And when you swapped the motor, did you make sure you had a good ground from the engine block to the frame, and from the neg. Battery terminal to the frame/engine block?

Get back with me and I'll try to walk you through your problem.

It'll be kind of difficult to provide you with accurate information with me not knowing exactly what was/wasn't done during your engine swap. Especially if I can't physically test your car's electrical system.

What you should do first is check to see if you have 12-volts at the interior fuse box's main power terminal, as well as a good ground. (Not just continuity but measure the resistance from the fuse box to ground)

If you don't have 12-volts, then you need to chase the circuit back from the fuse box to the bat.

Also, the computer that controlled your TPI motor also controlled some of your instruments/gauges/warning lights. Since you've disconnected this computer, it's hard to know what will be affected in the interior. (I don't have a complete electrical diagram of your vehicle, and it'd take me quite awhile to interpret one)

Hopefully another tech on this forum will have more experience than myself with engine swaps for this particular vehicle. Good luck!