/6 cost

So today I was driving around and my engine stalled. Stalled every time I took my foot off the gas. I brought it into a shop out on the side of the highway and had a guy take a look at it there. He told me that Id likely need to drop a new engine in. Said I was leaking oil from the head gasket and that all the repairs for the 225 I currently run would cost me more than dropping in a new engine.

I'm trying to make this car my daily driver. Nothing fancy...yet.

My question is, how much should I expect to pay for a rebuilt Slant 6? Where can I find them? If I go scavenging in the junk yard, is there anything I should keep my eyes open for? I don't have much to spend so economical ideas are ideal. Thanks a lot.