what is the diff between 351m + 351w pistons, is it the same size slug? can i put 351m piston into a 351w block? , see i've been looking into using 351m heads on a 351w? its just a crazy question! but while i'm at what is the diff, between the 351w +351m motor alltogether??

 

there are several differences that cause a few problems with your proposed piston shuffle. the compression height distances are different and the wrist pins being different sizes are the biggest problems. the valve reliefs are different and the distance to the top ring are different too.

with a moderate lift cam the W pistons will work fine.