Besides a possible increase or decrease in compression, would I really gain anything in the 2000-6000 RPM range by switching my stock "063" closed chambers to stock closed chamber rectangular port heads? I guess the valve size is larger and it might flow better right? 10-15 HP?

The question is, do I spend $500 on used rectangle port heads and a new intake, or just keep my heads?The motor is currently out of the car, so the swap would be easy.
Rick

Is this engine a big block or small block?

The motor is a 1969 427.

The square port heads will help you in the upper RPM range if you are going to add a large cam. Big blocks like to breath so the more air they can pump, the higher they will pull in the upper RMP range but you will notice it will be slugish in the lower RPM range. The square port heads and big cam need more gear to get the RPM up at slower speeds.
In my option with the 427 having a shorter stroke, I would go with the square port heads and add a large lift cam. You will need a low rear gear also, but the engine should pull strong up to 6500-7000 RPM. The low gear will help keep the RPM's up so it won't be slugish when the RPM's are low. Just remember that the more a big block breathes, the more horse power, period!
You might need to go with an 850 Holley also. It will need the extra fuel.
As for the amount of extra horse power, I would guess around 50.
Hope this helps, just my option.

Neal
'69 Camaro L89/396 4 speed

What are the rest of the specs of the car.

for street use stay with the oval heads. The 6000 plus RPM on a BB without a good balance job is asking for trouble. You will also most likly run into valve flot above 5800 RPM. remember one thing leads to another.

Thanks for the responses. The car is 68 RS Convertible. I just posted in this same forum about a few options I am considering. I would appreciate any feedback.
Rick