You can get 300 horse out of a teen pretty easy and with good heads and some compression (and all the rest of the goodies) 400 horse isn't out of the question.
Here's a stock low cr longblock with 4bbl headers and a comp xe262h cam making 282hp @ 5000 rpm, up the cr and probably hit 300hp then add xe268h-xe285h + for even more power before doing anything with heads.
I wonder what a 10:1 stock head no porting 318 would make with a comp xe285h or similar cam airgap 750 and headers would make ? my guess would be 330-350 hp at 5500-5700 rpm. Heads would definitely be the limiting factor.