1976 GMC C1500 She acts like a slug

I recently replaced the entire powertrain in my truck, to include axels so about the only thing left from 1976 is the body. 2 weeks ago upon completion of the re-instal I drove it around for about a week everything seemed to running out standing. I went out to start her the other morning the was no fuel in the filter>>> I cranked and cranked till she started with a little help from carb medic. I got the carb. Set finally (i think) and I think I may have a vacuum issue. When I put it in gear and take off she's loud and thunderous. Then she chokes like no tomorrow. Any ideas?