This is what I got from Ron. I have nothing to do with this engine or anything else of Rons .

Yes the 501 is for sale. It was in the Valiant for about 8 months and probably has about 20 passes on it. Plus about 300 street miles. But, it was hurt when I took it out. It had dropped a Valve/broke a retainer. So, I pulled the one head and the piston was ok and I had the guide replaced and replaced the VVs in that cylinder etc and put the head back on.

The thing is, the machine shop showed me where the valve seats were crumbling. Indy had put some cheap valve seats in these heads. I sent pics to RyanJ and he said to just run it. It also had some cylinder scuffing from the pistons rocking at TDC. (short piston with 4.5” stroke) He also said that would not be an issue. He said he rebuilt motors that had scuffing like that and they did not pick up much if at all and that I was probably not losing any ET to speak of. The day the car dropped the Valve it turned 1.34 60 foot time and would have probably run high 9 seconds but there were Santa Ana Winds so I was not making full passes. At Fontana.
So, I reinstalled the head and I was replacing the retainers on the OTHER head. RyanJ/CompCams sent me new ones. I put air on the cylinders to hold the valves closed. Well, the air leaked so bad out the intake ports it sounded like a Jet Plane. So I knew right then that the valve seats were not going to cut it. I pulled the heads off the motor and spent $5000 fixing them the right way.
The heads now have all new Xceldyne copper beryllium valve seats all blended in with a race valve job. All new Xceldyne bronze guides. New Titanium intake valves, new special alloy hollow stem exhaust valves, new Titanium retainers, machined locks and seals. The Valve springs are a Manley NexTec double spring. The heads were surfaced and installed exactly how I did the first time with Cometic MLS gaskets. The motor is all back together now and ready to go. I also put new pushrods in it because they had contacted the steel shim in the VV cover gasket and believe it or not that galled some of them so bad I was afraid of failure. It also allowed me to refine the length to get the adjuster screws in a more ideal place. I also put air on all the cylinders since reinstalling the heads and there is no noticeable air leaking any more. So I do believe the scuffing will not be an issue. I can give a lot more details if someone is serious and wants to call me. I have had the pan off to repair it after I smashed it doing wheelies (twice), so I inspected a few bearings and they were ok etc. I replaced the oil pump because the pressure gauge was acting a little weird, but that seems to have fixed that etc. I 100% planned on keeping the motor and running it in another car including a driver, but a lot of the cars I am looking at buying already have good motors. So I decided to try and sell it and see what happens. I think it would cost about $28,000 to build this motor now with the upgraded heads/vvs/seats etc.
I also have custom Headers I built for this motor that I have put a LOT of work in them to get the ports/flanges to match properly and they are ceramic coated. I have over $1200 in materials/coating! They were smashed but have been fixed/recoated.
The motor will come with the Vacuum pump and a one wire alternator with the mandrel drive as pictured. Everything else in the short block is per that thread on Moparts.