AFR numbers look decent. You might consider dropping a couple sizes in the rear to see if you lean it out a little at WOT. Also, what do your plugs look like right after a lengthy WOT pull. Kill the engine at WOT pull over and pull a few plugs.
Not knowing much about the rest of your engine, itís hard to say if your carb is too big. However, I would suspect it is entirely too large. I know guys running well over 400hp 289ís running no larger than a 650DP. Iím only at 350hp and use a custom 650DP.