The Stovebolt Site Forums The Shop Area Engine Shop 270 bogging me down

Here's my question, it's about what I need to do with my ol' beastie as I seem to be at a point where I need some advice.
So! I have a 270, it's in really good shape so far as the engine goes, recent refurbishing and a fresh set of seals. Stock exhaust manifold has a slight leak on the 4/5 flange but nothing bad, everything else is tight. New pipes, good breathing air filter, timing is dead on the ball at idle and winds up as it should, everything looks perfect.
At idle,...
Purrs like a kitten (a 8,000lb kitten, but yanno!) at idle and accelerates pretty well. Puts out a bit of smoke on startup, but I believe that may be oil gettin into the valves.
Where it's killin me is when I drive her. It's a little dodgy @ about 1500 RPM, seems to miss a little bit, but can get up to steam OK on level ground and runs pretty well. Then she starts to bog down a bit, MUCH worse if climbing even a slight grade, and I get some black smoke out the pipes. At it's worst it felt as if I was hitting on 2-3 pistons until I backed out of it and coaxed her along at lower RPMs.
Thinking I was flooding out so I rebuilt the carb (it's a Rochester C) and checked all the seals, float level etc. Put it back on, seems to be working great, until I get her on the road and expereince the same issue.

SO!
Here's where I am, I've verified everything is working and firing, just doesn't wanna run up all the way.
Thinkin I have too much jetting on the carb, that or the power valve is coming open and staying that way.
Or, I have a stock vaccum timing advance setup I can toss under my dizzy and see if that helps with my burn issue.

Any insights oh gurus of old iron?