1993 Chevrolet c2500 with 350 TBI.

Ran great, lifted the bed of the truck to fix pinched fuel filler line.

Set back down ran rough, smoked, no power-this prob a coincidence, but had to mention it.

After a lot of swapping and working, it will smooth out with low voltage.

 

Have you checked your ground connections between the block, firewall, and chassis? Check for continuity between each one. I have a similar truck. Perhaps you disturbed the fuel pump ground connection under the bed? If there's a bottleneck in the grounding system it may create strange symptoms when the alternator is attempting to put out a current and is unable to properly return ground voltage. I believe it is a 1-wire alternator like my 89' 2500. The 2-wire units use the second wire typically at a junction box to sense the voltage in the system to adjust its voltage accordingly. Start with checking continuity between grounds. You could also have the alternator tested.