Rough idle and takeoff 250 inline

[68gmcdude]

Engine is idling worse and is getting worse under load. I advanced running to 8⁰ from 6⁰ and then increased to 10⁰. No improvement. I took the belt off of the smog pump so it wouldn't run and nothing improved. The carb has a nice stream of gas shooting into the carb when I pump the accelerator. I'm thinking the old truck didn't like the long 400 mile trip on the highway. I had never driven it that far in the highway before.
I'm going to do a compression check next. Any other suggestions? I'm thinking it's just tied and needs rebuilt at this point. Only 56k miles on it.