Most popular tach in the 70's and other stuff

Oh BOY! .... like you're asking (what was automotive "fashion" in the '70s?
Well, P/S was HUGE then so a lot of guys tries to emulate them. To that end, you'd get:

Sun tachs, as mentioned (S-W was second)
Sun gauges with blue backlighting (looking to buy them now, BTW)
gold anodized valvecovers,
oversized rear tires (l60.15s if you could fit 'em)
vertical gate shifters (racing auto trans weren't fully developed)
"Lakewood" bolt-in roll bars
8-track players
white headers & undercarriage
solid lifter cams
Accel coil & wires
Mallory or Accel distributors
Cragar S/Ss in front, Ansen slotted wheels in the rear
hood scoops of various styles. Usually to copy the P/S cars
"Purple Hornies" glasspacks---Thrush 'glasspacks if you were poor
"flex-a-Lite" 'glass fans
'most anything by "Moroso"
pinstriping
cool-cans
braided lines (as it was new stuff then)
airshocks
bolt-on traction bars (usually "Lakewood"
NMW ladder bars
Edelbrock "tarantula" manifolds
(for Mopars) STR or Weiand manifolds.

Did I leave anything out!!:D