OK, you're trying to do this two different ways:
Initially, you compare the SB Mopar to the SB Chevy.
Then you start comparing it to the late model LS motors...
The LS heads won't bolt on a Small Block Chevy either.
First off, the LS motors are the top of the heap as far as small block motors go, like it or not. If GM could manage to put one in a car anyone wanted to buy, it would be more obvious.
The newer production stuff also has the advantage of better ring technology (less drag), and machining tolerances that your local guy is never going to beat. Also remember that the ports on these heads are only required to flow air, whereas old school small blocks have to flow air and fuel.
I think you're on to something with the weight issue, and there are a bunch of supposed advantages that the Mopars have that aren't really advantages....Like...
Gigantic heavy lifters. I suppose they might give "better valve actuation", but the brand X cars are actuating their valves just fine. Valvetrain weight is a huge concern for RPM production (which is how small blocks make power). Racers fret over Ti retainers and beehive springs to save grams, and we're stuck with these lifters that way ounces more.
FYI MOPARS SOLID LIFTERS ARE HOLLOW WITH A CUP & SNAP RING AND WEIGH 20 GRAMS LESS THAN ANY TRADITIONAL CHEVY/FORD/OR EVEN THE AFTERMARKET COMP, HUGHES, ETC, LIFTERS.
I don't really think the shaft rockers are an advantage. You can spin stud mount rockers really high without trouble (in my SB Ford, I ran 7/16 stud mounts 8000 RPM in NMRA Pure Street competition *without* stud girdles). Stud rockers have a big advantage in that its cheaper and easier for them to improve what the factory gave them than it is for us.
THE PEDESTAL DESIGN IS BETTER THAN STUD AND NOT THE SAME AS CHEVY.
MOPAR CRACKNUM'S USE THE PEDESTAL ROCKER AS WELL.
Valvetrain Angle; Well, that's an advantage, as it can move air more easily, but it can only move the air that gets in, and the problems with Mopar heads are widely known...same thing applies to big valves.
THEY GET IN A LOT OF AIR COMPARED TO ANY OTHER SB HEAD OF THE SAME ERA WITH THE EXCEPTION OF THE 302 BOSS=4V 351 HEADS WHICH HAVE NO VELOCITY TO MAKE USEFUL ON THE STREET SO WHO CARES.
Thermoquads? If I want to make power, I'll go for a Holley every time, cool fuel or not.
I AGREE!
As you mentioned, rotating assembly weight is also a huge problem. There are huge gains to be had in dropping weight here.
340'S HAVE LESS STROKE AND HAVE NO PROBLEM REVING FAST AND DO IT LONGER!
Lets not forget exhaust, either. The A body wasn't designed with a V8 in mind, so the header options aren't as good as they are for most GM and Ford stuff.
SB MOPARS BENIFIT MORE FROM HEADER TUBES THEN SB CHEVYS DUE TO THE OVER SCAVENGING PULLING THE MIX SO HARD THAT IT GO'S RIGHT OUT THE EXHAUST & TAIL PIPE.
Timing control is hugely important for power production, and WTF is with the distributor on these small block Mopars? Whose idea was it to set that up?
WHATS WRONG WITH THE DISTRIBUTOR[ROTOR CAP PHASING]
THAT THEY HAVEN'T FIXED IN 2002?
I think a lot of this has to do with the fact that Chevy (and Ford) put a lot of priority on their small block design. GM invented it after all. (and this is doubly true of the LS motors), whereas in the 60s Chrysler was concentrating on the big block stuff.
Don't get me wrong, I love my Mopar, but I'm not going to be in denial about its limitations.