[lolife99]

Wheels will depend on the look you are going for.
I personally like 20's,... but the width and backspacing still applies (for the most part).
Your '72 will have the wider rearend housing.
Member hot trux just installed 20x8.5 (5.25" BS) Boss 338 wheels on his '68 (with a 71-72 rearend).
These wheels fit perfect inside those tiny stepside rear fenders.
But if it was a fleetside truck,... a 20x10 (5.5" BS) wheel would be better for that bed style.