Welcome Mike,
There are several Great fabricators here who may be able to save the head for less than the cost of a new one. If you're not in a big hurry to get the 500 up and running you can always bide your time and keep a look out for the parts you need to get her up & running for a reasonable price.
I'm afraid once you get the big bore bug it will be hard to shake.
I agree with the tear down of the 500 engine to see exactly what you'll be up against as far as any "Hidden" problems that might be lurking in there.
The gaskets and consumables run around $100.00. Rings are around $30.00
Fork seals, cables, brake shoes, grips, etc all add up. as I'm sure your well aware.
I think a little bit of snooping about the site should give you a pretty good Idea of what it will cost to do a good run through the engine.
Should you decide to accept this assignment... I would recommend a stock re-build to get a good baseline and keep the cost down.
Get the old girl in good tune and I think you'll be quite impressed.
I don't have any disposable income myself right now either, so I know how tough it is to see a bunch of parts about the garage and not be able to get it all together.
Welcome aboard,
Tuck\o/
