You'll probably want to stick with forged for that 650 HP, just to give margin in case 'stuff happens'.
Chevy pistons are typical shorter due to the shorter block heights.... Mopar blocks are taller than most. So it takes some time and work make thing match up.
Small block chevy pins are typically .927" diameter, versus the larger .984" of the SBM. So you are going to have to find a way to bush the SBM rod to a much small pin. I've been figuring out a similar change in pin size and the standard rod bushings made by the hot rod manufacturers are thin-walled and don't cover that range of smaller ID to larger OD. The only thick-walled off-the-shelf bushings close to the right size (that I can find so far) are all C932 bronze, which is softer than the silicon or silicon-aluminum bronze used for performance rod bushings; those are made from C954 or C642 bronze, and for your HP use, I think the harder bronze is a necessity. So unless someone else knows of a silicon bronze thick-walled bushing close to the right size, or has some other trick, you would have to get some 1-1/8" OD x .125" wall thickness bronze tube of the right material, and have the bushing turned on a lathe. Certainly doable and the material is available.
Bottom line is that if you are going to use Chevy small block pistons, you may be better off to use Chevy rods too, so that the pin bushing is already the right size. There are chevy rods for 2.100" journals and 2.000" journals, which require your crank rod journal to be turned down .025 and .125" respectively. The one thing I recall on most Chevy small block rods is that the big end is a bit wider (like .010" or .015" wider).
As we say over here... there's no such thing as a free lunch LOL
