I think the ultimate fun and reliable 318 is the one you have that was cheap :lol:
That being said, I think my 318 was damn strong for pretty cheap. and a screamer now for just a little more money.
In high school it had a comp 265H with .465 lift and 265 duration with $50 headers I got from a member here and a stock 1971 thermoquad manifold (with a 600cfm QFT marine carb.-later a 450cfm) I semi ported with some hand filing. The engine itself with a trans was 200$. just that was able to outrun a classmates 370z. Got into some **** with that setup.
Now, It has speedmaster 170cc cylinder heads on it (non ported) and a Torker II I ported and stuck on it. It has an Isky .505/.292 on a 108lsa in it; revs out to 6700, probably more when I get stiffer valve springs. It also helps that it has flat tops and 9.08:1 all said and done.