Couple questions:
The manifold you mention is for 4V heads. Aren't the Procomp 3V heads "2V-like" port size? Further, don't the Procomp heads have the intake port raised? Maybe the 4V on these heads will take the port raise up, but there would be a hellacious port mismatch. That has been done before, back in the day before 4V for 2V heads manifolds were available, people used to put the stock Ford 4V manifold on 2V heads and it worked. Less than desireable, but worked.
Interested to know what you encountered in this regard, if you chose Procomp over Edelbrock and why. Are they a lot cheaper? I don't think so, but not sure if you compares apples to apples.
Also, what rear gears are you running? I really wanted to run the XE274, but don't have a 5 speed or the gears needed (3.73 minimum recommended). So, I had to let sound reasoning be my guide and backed down to the XE262 until such a time that I see my way clear to the required gears (I chose 3.25, again sound reasoning) and a 5 speed to go with it.
Please don't get me wrong, I am not ripping on your engine or anything, but as a fellow "Cleveland guy" I have a few questions.
Regards,
Bob