Good score. What heads are you planning to run? What are the plans for this engine? there a re a few ways to raise it. All but one lead to having to spend $$ to "fix" a situation cuased by the change.
You can reduce the head gasket size, from factory .040 to MPs .028. It doesnt give a ton, but every little bit adds up.
You can take std X,J,O,915,308 heads and mill them to get a smaller chamber. They are almost always bigger than factory spec 68-72ccs. Closer to 76-78cc normally before milling and new valves. So, you can have them whacked a bit. Anything less than .030 isnt really helping much, and IMO not worth the extra cost. You also must mill .009" off the intake side of the head or the intake itself for every .010 removed from the deck/head surface. You cant mill more than about .030" off the intake side before your valve covers dont seal well, or the bolt holes for them are made very thin on the intake side. Also, excessive milling can cause preload/pushrod legth issues, and rocker geometry problems too. These can be overcome with new pushrods, and/or rocker shaft shims.
You could mill the block's decks to below blueprint spec. Same milling required to fit the intake, and pushrods/rockers.
You could run the 68-71 318 heads. Smaller ports, but with porting, 1.88/1.60 valves, and a good valve job, the 62cc chamber will give a good bang for the buck. But they do limit power over 5500 on a 360.
You could replace the heads with any Magnum type head. They are 58cc chambers, have decent valves, 1.6 rockers, but will need pushrods and the intake manifold holes redrilled. They also have some minor cracking issues.
You could take this route...Replace the pistons, and have it internally balanced. Hypers are normally my first choice for budget minded general performance. But, they need to be fit proiperly to the bore. This block was already honed, so a forged unit would make more sense. (they run wider wall clearances). The problem with stock pistons, aside from external balancing on the 360, is they have no valve releif. So, as you increase the compression by moving all these parts closer together, you loose the ability to run decent cams. If he bought it right, grab a set of forged flat tops, and have it internally baalnced. That's the best way.
I took the buget route on a 360 I have. '87 truck (mopar rebuilt) short, .040 over, pistons like .080 in the hole IIRC. I took a set of '70 318 heads, ported them to 340 intake size, bigger valves, and, milled them .050. With the MP gaskets, it's 9.8:1 static, runs the XE268 cam and a sinlge plane torker. It idles at 700rpm, has a slight romp to it. Pulls from idle to 5K really well, then peters out at 5500. I needed the intake milled, and I shimmed the rocker shafts up to set the lifter preload. The milling, shims, and gaskets ran about $350. I still have a factory balance (yuk) cast stock piston 360. For another $300 I could have had a real stout shortblock.
