Several things I see here, some have been mentioned already.
Compression ratio is too low, why are the chambers 68cc? Many 23º heads have smaller chambers. 18º should be around 50cc or less.
Cam is not what I'd choose, but probably not killing 150hp either. More exhaust duration and wider LSA, but get the compression up. Lift is too short, mainly from low ratio on rockers. 1.7 or more on intake and 1.65 on ex would have been better.
Who ported the heads and where did the flow numbers come from? Heads have the biggest potential for killing 150hp. Improper porting or someone giving incorrect flow #'s can make for a really weak engine. Are these the raised runner 18º heads?? The bottom of the intake port is about 1.25" above the deck.
Dart intake, ... not sure if this is the same one I looked at a few years back, but that thing had runners so small it didn't even have enough metal to make it the size I wanted and I was running a 360ci 18º. I sent it back and got an Edelbrock, then spent a ton of time opening it up to a reasonable CSA. If the heads flow good but you put a small intake on it, it wont make any power. To make 750+HP, you will need 3.5sq.in CSA or more.
6AL ignition on an engine that should make well over 700hp??? Get a better ignition for it, especially if you find the problem and it starts making the power it should.
I built (8-9 yrs ago) a 360ci 18º engine that dynoed 750+ @ 8000. Heads were Dart that I ported myself. They flowed pretty close to yours 358@ .750" and
[email protected]". With 75 more cubic inches, that should make more power and do it a lot lower rpm.
Rick