It hesatates when youhit the gas under low rpms

crankshaft position sensor

I have had a similar problem and it turned out to be my idler air control valve. I temporarily fixed mine by adjusting the idler screw under the hood.

do you smell fuel?

I would check for any vaccum air leaks around the intake. That is a very common problem on these engines that makes people spend tons of money. Does it throws any codes?

Low fuel pressure, a faulty throttle position sensor, faulty temp sensor, or vac leak among other things.

Sounds like a fuel filter or fuel sencer or maybe just a good tuneup

I'd be curious to the miles on the engine, possible worn rings, poor compression. Start with basics first, be certain there are no vacuum leaks, next look to your fuel system; possible failing fuel pump (low fuel pressure) dirty fuel filter? (I'd start with the filter first, cheapest fix if it is the issue) other concerns could be injectors, plugged or failing (poor fuel spray) run a fuel systems cleaner for several tanks see if it will improve; but change that fuel filter first. Also the volts dropping off would make sence if the engine RPMs drop way off, too slow of a speed the alternator will make little if anything.
I hope this may have helped,
Tom

Check for a loud hissing sound under the hood, f a vaccuum leak is suspected. If not the check for proper fuel pressure and volume.

It could be a acceleration pump problem, or it could be that there are larger jets in the back carb. witch could make it hesatate when the secound carb. is starting to come in. Also holleys are a tempermental carb. and climent has a lot to do with there performance. You also might want to chk. the flote level, to low can cause it to hesatate.

my truck did the same thing a while back and i repleced about everything only to find out that it was the oxygen sensor. This is a very easy fix and fairly cheep. Hope this helps.