[71gp]

Thanks for all the great responses, It's helping me add to my knowledge of all things carburetor related.
I talked with Sean from SMI who was able to impart some great information that has eased "some" of my bad attitude about Q-Jets. Plus, many of you have reported some good results with them. Apparently, getting them properly set up is the key to having them run well. But that's the trick - proper set up in the 1st place....
My concerns about clearance issues (if I go with a Holley 4160) are all manageable. Holley (according to their catalog and application charts) no longer offers any "spread bore" carbs (like 4165 or 4175) for 70's era Pontiac 400s. Just the "square bore" 4160 which I have. They seem to focus mostly on Chevy applications.
So My thinking on this has evolved (with your help) into this:
Plan A: Install the Holley 4160 & related equipment. Being done by very experienced pros at a top-rated shop here in Rochester. Will tweak whatever needs it, and tune it so it won't run too rich and kill my (VERY Expensive) Gas mileage. Yeah, I'll probably have to modify (cut) the original carb to fuel pump line, but heah, that's a catalog item and can be replaced.
Plan B: (Because it always pays to have a Plan B) Save the original Q-Jet that comes off the car (including the dual snorkel air cleaner), and have it "re-manufactured" (Hello, SMI) or replaced with one of their Pontiac appropriate units (335007), which ever works best.
How ever it plays out, feel free to speak up and let me know if you think I'm on the right track.
Thanks again. I look forward to your continued input. I'm going for my degree in carburetors !.
John