HELP! Blown 4 regulators-cannot get a charge

I have a 1988 Suburban, 350 TBI, Silverado package. After dropping in a rebuilt motor, my alternaotr stopped working. I have replaced the altenator 4 times, the starter twice, battery and posts once. Cables and connections are good, voltage to all areas with volt meter and test light. Witht he battery at 12.2-12.5 volts, motor starts and runs, but voltage drops .5-.6 volts.

I have been through 4 altenators and have fryed all four regulators. the last one was a single wire altenator that picked up the voltage from teh single post abttery connection. The last 2 units produced a maximum of 13.5 volts for 15 seconds, then dropped back to 12-12.2, then right back to 11.5-11.8; never to produce a charge.

I have checked all the connections, ran a jumper cable from battery pos to BAt terminal on altenantor and nothing works! I need to get the truck back on teh road ASAP, my father totaled my wifes car and she needs wheels.

Any help would be GREATLY appreciated, I am at my wits end!!!

check negative and positive battery cables, also check for a bad ground.can't beleive no one would help you.