Yeah but you can put a 340 callout on the quarter and run a 318 or a 360. With a 4 barrel and headers you can't tell the difference unless you actually look at the numbers on the block. The 340 in my Duster doesn't look any different than the 318 in my Challenger from the outside.
I'm surprised that 360's are so hard to find and expensive for you. They're not super common around here on craigslist, but the later trucks and vans still hit pickNpull frequently enough. I probably couldn't get one tomorrow or maybe even in a week or two, but I bet I could source one for under $300 in a month or so. I've paid as little as $50 for a 360, and that was a complete standard bore, original longblock. Granted that was 5 or 6 years ago, and was a bit of luck as I was there to buy other parts when it was offered to me.