That was the bad news.
-Heres the good news;Forget; the 750rpm idle and the 4400rpm peak power,and that cam, and the 9:1c/r.
- Firstly,will your outdrives and props support more engine rpm?
-If no, I see supercharging in your future(not a bad thing).
-If yes;youre going to need more engine rpm. Probably 5400 with 400ish cubes. Then you work the formulas backwards as to headflows,camshafting,Dynamic C/R, and finally Calculated C/R.
-Then you find somebody to build it, so it will last.
-This requires professional helps and gobs of cash.
-And I would not mention anything to the professional builder about a budget. Budget motors blow up.
-Now, getting back to supercharging. Somebody remind me: Just how many guys here have pulled 400 hp-plus, out of a bone-stock 5.2l/318s. Now, since you have the 5.9s, 450 is pie.Maybe even at 4200rpm. NO; fancy heads,big cams,expensive porting,C/R manipulations,outdrive gearing,re-propping,etc. And if the engine blows, heck, keep spares with all the cash you saved.And bonus they idle at 750 or even less.
-Thats what I would do.Uber duper Supercharging.