Those numbers seem about 100 HP too high?

In most cases, you would be better off using the 512 cid stroker kit. The smaller rod journal size and rod bearings make the kit fit better than the Mopar sized rods.

On the 4.15 stroke / 499" kit, I have been running one for awhile and haven't noticed any issues, but It is coming out of the car this winter to be freshened so I will check for piston wear.
Not sure if your building for street / pump gas, or race / race gas?

The ring support on the 499" kit is nothing to worry about, except to check there are no burrs around where the pin was machined. I had that issue, the ring support was not sitting down flat, and the oil rings were too tight.
Easy fix to de-burr around the pin holes. That was the source kit with ICON pistons.
When I built my 499 with 440 source kit, only the pickup tube boss needed to be clearanced. Not sure if the different year block has anything to do about that. I used a '71 230 block (wasn't looking for that specifically, just happened to be what the guy had when I bought it?)