451 stroker, cut the crank or block?

The weak spot is the block. So I would cut the crank. You mention not having money for the stroker kit... The stroker crank itself may be cheaper (Brandon's anyway) than the machining on the factory one. Especially if you are knife edging and adding big radii and lightening. The new crank in a better material is $600 plus shipping. The last crank I had done without kinfe edging or lightening, but having it indexed and corrected, plus the turn and polish went $350. I havent had a forged crank that needed to have the counterwieghts cut down to fit a B block, but I've heard of a few that did. Also, dont go too light or you'll be adding metal to balance, for more money... If it was me I'd just have teh mains and rods cut, then test fit it to make sure the counterweights are ok. Run it that way. You wont break it...