That "external EGR" idea is going to be a lot of work for no tangible benefit. Just delete the EGR system entire and recurve your distributor (good excuse to do the
HEI upgrade ) for optimal advance.
Those "reproduction" carburetors are a primitive, not-very-good, grossly overpriced option and they aren't very compatible with your '75 car. Two matched new (not "remanufactured") 1945s will be a very good pick and will simplify the installation with their built-in throttle return springs.
Get a № 1234
electric choke kit and make a new pushrod for it as described and pictured
here.
All that said, unless the primary main goal is the "Wow, cool!" factor when you p
See
this thread for kickdown options.
You'll need to either use the '63-'67 small/tall (9") air cleaners shown in Jim Kueneman's post, or fabricate your own air cleaner. If you fab your own, you might build it around the oval filter element from a 2-4bbl or 3-2bbl setup. And that would also let you keep the very beneficial thermostatic snorkel.