[Bernhard]

I would say no to the fuel cell never liked the look myself.
New stock tank would be my vote.
sump added to stock tank not a big fan of this look but it was common. Fast cars ran this setup.
Auto meter gauges with hood mounted fuel and oil.
I would use a standard auto meter tach with no shift light.
Centerline rims are a must have and you have that box checked
Holly fuel pump yes
Aftermarket period correct intake.
Ladder bars were on the way out in the late 70's air bags, boxed control arms,no hop bars were in.

factory hoses with original clamps and or worm clamps except for the fuel line
fuel line was braided. Some guys went all in on with the braided line. They were more show than all out quick street cars.
Chrome hinges and shroud cover were in.
Valve covers M/T never go out of style
Moroso water pump drive was in as well as cool cans.
Larger alt pulley Moroso or factory.

Your Chevelle is very cool build.