It will look good and proper. If you can get the correct 2x4 "big"
I have the 2x4 on my nailhead and while troubleshooting a "hunting/rough" idle, i pulled the 2x4 and put on a Quadrajet intake and carb, and with the Q-jet dialed in, it is like a different car. It runs smooth and transitions correctly from idle though WOT, and all variations, as well as up and down shifting. (manual trans) But it just doesn't "spank it" like the duals.
The power difference is very noticable using my "Mk1 Mod2 Butt Dyno.
The 401 loves that 2x4 setup and I will be putting it back on after I make sure the surfaces that meet the heads are straight. (the heads are nice and flat and smooth, but I suspect the intake surface needs to be flat filed or machined.
Anyway, if you can locate the correct, large air filter housing, it will look "correct" as it should (not purist, but period specific).
I elected to go with finned aluminum. I have never been a "bling guy", and always preferred function over form and "go!" over "Show", but the nailhead is like a Barbie doll of engines and begs to be dressed up.
If you go with the 2x4, tap the exhaust ports in the intake for the primary side of the rear carb and put in 1/8 NPT plugs.
(mocking up)