360 Magnum building on an existing bottom end

I would replace the rings, rod and main, cam bearings.

I did that with my 5.9. The engine I bought had 80K mikes and looked much better than the OP's. Still wanted new rings and bearings.

I dropped off the short block to a machine shop for hot tank, crank polish, hone, rings, and main, rod, and cam bearings. But that ran $900 three years ago.

I used stock pistons and Rods, but replaced oil pump. Then spent $$ buying a new top end. Sent my cam to Oregon Cam Grinding for a regrind. I reused stock lifters. Runs like a raped ape!!