Help with my first engine build (5.9 Magnum)

I hope it's not too late and I didn't read the whole thread to see but are the factory roller lifters in good shape? If so I'd highly recommend reusing those with an aftermarket hydraulic roller cam. If you get a "retrofit" roller cam it'll have the extended snout to run a mech fuel pump. Flat-tappet cams work but if you can use a roller cam without having to buy all new lifters that's the way to go IMO.

The engine in my Duster (avatar pic) was a high-mileage 5.9L Magnum I pulled from a truck at the local junkyard. There was a tiny bit of wear on the cylinders where the crosshatch was more faint near where the head bolt bosses are but overall looked great. All I did was replace the rod bearings as they were showing copper and "sent it". Majority of the money I put into it was for the top end (heads, cam, intake), reused pretty much everything in the short block including lifters and had a roller cam custom-ground by Jim at Racer Brown. That was about 4 years ago, still runs like an absolute champ with minimal blowby and put down 290 HP at the wheels, uncorrected at 5000' elevation. I think 450 HP at the crank at sea level would be a safe estimate.