Acceleration and Stalling Problem 72 GMC

[Thatguywithaneye]

So I recently got my 1972 GMC Sierra Grande and it had been sitting for a year and it had a terrible transmission leak so I took it to a local shop and had it rebuilt. I had only ever driven the truck twice (once a test drive around my neighborhood and the other time was to the tranny shop). Anyways I noticed the truck seemed a little under powered, but nothing too crazy.

Problem 1:
When I picked the truck up from the shop it stalled 3 times getting it out of the parking lot. The truck has the 350 engine and the TH350 automatic transmission. It was idling fine, but as soon as I put it into gear it would stall out. This had never happened before. I eventually got it off and away, but the troubles didn't stop there.

Problem 2:
As I was driving I noticed a lack of power and responsiveness. When my foot was completely on the floor It would either take off like normal or do nothing. The worst of it came when I had to climb a hill up to my neighborhood and I could barely make it up...It would not pick up any speed. As I crept along the last corner of the hill (about a 2.5 mile hill) it was at a mere 6MPH and I was in fear of it dying. Once it started to flatten out I got back up to around 25MPH.

Problem 3:
While all of this was happening there was a loud ticking sound (no not a knock) a tick or tapping sound. Not sure if related, but it was prominent coming up the hill. The truck was obviously also really loud.

So the truck has been sitting for around a year and the gas in it has been too and I'm honestly not even sure how much is in there because the gauge doesn't work. I'm not sure if that would make a huge difference or not, but the oil is in the same boat. I'm just learning about all of this stuff so anything would help.