MPs method of correcting the RB sized counterweights was to stop selling that crankshaft. Stop selling the part, problem solved. Just being honest. Plan on either putting it in a lathe or working it by hand.

I'm using a reworked OE crank in mine, which I reshaped the counterweights using a homemade template + a series of grinding and polishing up the counterweights. It was an 80 dollar swap meet crankshaft that I paid another 90 dollars for machine work, 25 to mag, and the rest I did myself.
I wouldn't really recommend anyone else do that, but I was a broke musician at the time and dont mind doing tedious stuff like that.

I would have to have some idea what the goals are, and what the budget is to really make any recommendations on the combo, how to buy pistons, what to look for etc.

My own goals for my 451 was ballpark 600HP flywheel and high 10s. I've got the first one (499rwhp), and hope to make it to the second goal this year. It's also a pump gas street car that started with 3.91s, but now has 4.10s, and is driven for hours at a stretch on the street...