Everyone has their price and a friend found mine.
I am flying back up in a couple of months to help a friend swap engines in his old truck. A 1980 Chevy C10 with a 400ci engine. So, I need to source an engine.
Anyone have any ideas where I can find a good rebuilt long block? Stock or at least close to stock. Preferably deliver to Jefferson county area.

Many moons ago, I got one rebuilt at Shreves in St Louis. That's the only place I know.

https://www.shrevesengines.com/

Need to know more about the wants and needs here and overall project goals

1. Whats the end goal of this truck?  hotrod?  work truck? cruiser? or just a reliable carb'd V8?  Is fuel injection an option?
2. price range.  What's the total dollar amount that we have to play with here?
3. Does it have to be a 400?  can a 350 work if it has the same HP?
4. Are you looking to keep it old school stock or do we have the option/know how to say install a used LS 5.3L?
5. what transmission is going to be used?

Talked to Shreve's on the phone today. Looks like I will just take the old engine in to them and they will rebuild it.
Nothing special, just repowering an old truck to last a few more years.

A used GM engine from a newer truck (90's) will run better, perform better and only cost you about $500.  I wouldn't waste my time with a 400 sbc.  I'd get a newer style roller block 350 and use the vortec heads and EASILY make 300hp and have the engine feel / perform totally stock.  I gaurantee it would be the same cost as a rebuild on a 400.  You could also run fuel injection SUPER easy.