Well, your car was smoking, had guide issues and wouldn't rev. I don't think that makes for a scientific comparison. I'm not saying your car isn't working better with the Edelbrocks, but I don't think the comparison is valid.
I also had valvetrain issues with the Iron Rams I got. Then I discovered the cam I used required longer pushrods, but I eventually got it sorted.
My Iron Ram heads measured between 58 and 59cc out of the box. I ran the skinny 318 style gaskets with these to try to overcome the stock Magnum pistons being .050 in the hole...
My cam was 224/230 and with the Iron Rams/Air Gap the best shift point was 6200 RPM.
I actually sent back a set of Edelbrocks to run the Iron Rams, based on the significantly higher flow numbers reported for the Iron Rams in the magazines and on Hughes' site. Personally, I'll take a higher flowing set of irons over aluminums any day.
Given the lower flow numbers of the Edelbrocks, I don't see my car having picked up ET based on the aluminumness of the heads. Especially .3-.4
I'm a user and fan of the AFR 165,185 and 205 heads on Ford 302/347 combos.
Unfortunately, Edelbrock isn't AFR. The Edelbrock Mopar (or Ford) heads aren't fit to carry the jock strap of the AFR Ford heads. Nobody fast runs Edelbrock heads on their Ford.
I sure wish you could get bolt-on heads that work like those for Small Block Mopar!