Technical Two SBC head numbers: One any better than the other?

I have a fresh rebuilt 350 with head casting 3998991 (70-76 307-350, 1.72 Int, 1.5 Exh).
Acc. holes in the head

And a set of fresh LOOSE heads with casting 3884520 (62-67 283-327, 1.72 Int, 1.5 Exh).
No acc. holes, typical early “Power Pack”

Is one better than the other, ports, flow or chamber?
Will the early PP head work on the 350? (No acc. holes for early look) or is the chamber too small for the 350 cylinder?
Looks like the later model has a lot bigger chamber.
Thanks!

 

Depends on the rest of the engine....you didn't mention which 350, what it's in, what the goals are for the car, etc. The heads will fit and work, the compression is the big issue, most likely. If it's a smogger dish piston short block, and you're putting it in a well geared light car and don't mind buying premium fuel if needed, it should be fine.

Although we'll ***ume that you're not real interested in performance, since you're choosing between two different low perf heads (in the 350 world, anything with a 4bbl on it needs 1.94 valves)

 

If using flat top pistons, I’d p*** on the PP heads.
Probably p*** on em with dish pistons.
If the goal is just to drive something then I’d go with the 991s.
But honestly I’d find some 1.94 heads

 

I’m sorry, forgot the pertinent info.
I WON the 350 at a run. casting #14093638. 87-95 one piece seal. Haven’t checked the pad number. Probably (?) flat top pistons.
Cam is a “RV”.(Whatever that is.). Edelbrock ESP intake.
Built by a local established auto machine shop. Looks like they used what was donated/available.
Possibly going in my 40 coupe, mated to early trans. 8” rear 3:00. Street/highway driven only

 

Bolt it in and run it; you can always change it later.

 

You might want to think about a set of heads with hardened valve seats or do the 991's have them?

 

sounds like you want to use the later heads, with lower compression....

 

@squirrel
As this point, I’m wanting a little KISS. (Keep it simple)
The 283 I wanted to swap in to my 40 has an unknown knock.
I’ve have this fresh 350, just haven’t dug into it. Needs a flywheel, water pump, carb, ignition. Looks like a low compression smog motor from the numbers. The 991 heads are already on the 350.

 

Probably best to leave the 350 as is....see how it does when you get it running.

 

The early heads have a 60cc chamber and the later heads have a 76cc chamber. If you're content with the low compression setup, leave it as is and run it. But if you want it a little ****ier, have the early heads gone through and put larger valves in them with hardened seats and bolt em on.

 

Thanks all.