There are limits on pump gas as far as compression and returns and iron heads. I would shoot for 9.0 to 1 but if you have tuning skills, can push 9.5 or 9.7 to 1 with dialed in timing and jetting. Over that, you need to blend fuel, not a good idea for a daily driver.

You will not get the 10.75 to 1 330 HP number published running lower compression with iron heads. I say with an old, tired motor at safe compression....you'd be 25-30% less.

I would start with checking the engine health before investing the time and money. Do a compression/leakdown test...Possibly find a local guy who only tunes older cars and has a dyno and can give you a real world idea where you are starting at. It is an additional expense, but knowing where you are at can be very advantageous. I have a local guy here who is so OCD and ADD he can blow my skillset out the door and dial in another 30 hp.

Just my opinion, I would have the heads rebuilt, have the heads ported and chambers polished (mild) have the chambers deburred, all sharp edges rolled back, go with an 068 regrind, change the intake back to stock and get a q jet. I love the intake (allbeit heavier) and loathe Holleys and tuning them. I prefer a Q Jet...but that's simply preference.

However..I am kinda weary going with a hotter grind in a daily driver. You'd want to confer with Scott Esterle at Summit Racing in Tallmadge OH for a cam selection for your trans, rear gearing...or scour the boards at Performance Years. There are way more test and tune guys over there. Also, pick up Jim Hands book How to Build Max Performance...as well as Pete McCarthys books. Any other Car Craft/Hot Rod reference material or advice is crap. Also check into the High Performance Pontiac website.

I would also switch over to HEI or Pertronix in the distributor and have the distributor rebuilt and dialed in. I would also invest in reading the above material.

In short, and I speak from experience and hearing stories and highly regard knowledge over trial and error if you work hard for your money. You can realistically spend 10k on an engine rebuild INCLUDING mistakes, redos (R&R of engine and trans) mistakes, goofs, what if's...Or you could realistically spend $6000 for the same engine including pre and post dyno time, post tuning time, head rebuild and porting, cam..all hard parts, carb and rebuild, long branch manifolds, oil filter adapter and angled housing.

Or if originality is a non issue..you could get the Edelbrock RPM 72 CC heads CNC ported for $2500, Edelbrock RPM cam/lifters, RPM intake, Q jet or Edelbrock carb, good set of 4 tube headers for roughly $4k. You'd be at 10 to 1 compression, lighten the front end 100# and probably be at 350-375 HP. Then, if the block needs a rebuild, you would be ahead of the game so to speak.

As well, Jim Butler and Jeff Kauffman have some awesome Aluminum heads and the supporting knowledge to choose the proper cam, lifters, rocker ratio...and all other requirements for your build. They also port stock heads. If I were you...I would go that route.

You could go with a roller cam and get even more out of a 400. But they are a PITA to keep adjusted. You could also go with a stroker kit and get even more but that requires a complete rebuild.

If you want a solid, stout, well performing engine, it's gonna cost money and time. I got the time...just not the money.