Is the magnum rod 6.125 ?
Factory SBM rods were 6.123 ,,,,,at least all the old stuff was .
Do you need to cut both valve notches,,,or just intake ?
Either way,,,,I believe what you did on the piston in the pic will be fine.
Looks good,,,,,I think you will be in good shape .
It’s just the intakes that I’m worried about as the valve size is a big step up from a stock magnum, 2.055 vs 1.88 stock. But I will for sure measure both when the time comes.