Help with small block timing gear carnage

[JFC10]

Hi all,

I recently pulled the 350 out of my 69 C10. I was informed it had low compression, skipped timing chain, and various other issues (fully trashed) by the local small town shop. I have paperwork from a rebuild from 1987, although I realize that means nothing at this point. Since i would have it rebuilt or build it myself, I figure I'd inspect for damage; it had to come out regardless, right? Out comes the hoist and engine stand, followed by a record 2 hours of thrashing.

During damage control I found bits of the infamous nylon timing gear teeth scattered around in the lifter valley. I pulled the timing cover to reveal the broken teeth and a chain I could remove by hand. The thing is fairly crusty inside, valve stem seals and intake show signs of leakage. Despite my best efforts I cannot find a definite answer about wether or not a stock 350 chevy circa 1969 is an interference motor. It would sure be nice if it wasn't; I'd slap a timing set on it and throw er back in...

So I decided to test for bent valves, which would normally be accomplished by pulling the heads. Instead I like to do things the hard way and removed the check valve from my compression tester, screwed it in each spark plug hole, and hooked it up to a hose from the air compressor. Theoretically, air will leak past any bent valves and out the exhaust/intake. It was also entertaining to turn the engine over with compressed air, hear the air hissing past the rings, and tap the valve stems to produce a puff of air.

Well, it does leak, in EVERY one of them... Some more than others, intake and exhaust. Although my test probably isn't very scientific, I thought it would still be obvious which valves bent. Examining the valves, I see they are very crusty, and I would assume that because air is very thin, it would still leak past the smallest seam created from crud on the valves/head; which would otherwise let the valves operate without issue while running. My question is, (if you made it this far, whew) how much air should be leaking past the valves? Either every valve in my engine is bent, or a small amount of air will leak past in everything but a newly-lapped valve. Again, they all leak somewhat, a few more than others, but it's impossible to tell the difference.

I know what the right way to do this is, but I am just trying to get it running good enough to sell, as money is very, very tight. I'm not looking for suggestions on what to do with the project; and I'm sure every one of them is more expensive than a timing set and some gaskets, although I will listen to most with interest. A $500 craigslist engine was the previous plan after all. My level of caring is pretty low for this engine already, as it has been sitting for 4 winters. Assume I know nothing, and that my knowledge on engine building is little to nothing. Just looking for an old, wise gearhead's opinion on what a bent valve really sounds like when you shoot air in the cylinder.