The key for running .5-ish under for cheap money is finding combos that are kind of soft and where both the cars and the engines/parts are cheap and plentiful.
There aren't a ton of those if you're talking vintage mopars.
Find a decent southern rust free 64-70 4 door or wagon b body, put a 4bbl 383 in it........should be able to get it .5 under without any exotica.

360 4bbl Mirada's, volare's, and dart sports are another good option.


Brand x stuff........ 4 door or wagon 1978-1980 vintage malibu's with 4bbl 305's.