whats the stock diameter of the journals on a 71' 396 crank

Mains are: 2.7487-2.7496 (#3-#4 2.7481-2.7490, #5 2.7473-2.7483)
Rods are: 2.199-2.200
Side clearance: .013-.021 (solid lifter .019-.025)
Crankshaft end play: .006-.010

so if i'm .020 under is that gonna be for the rods only, or the mains too

.020 under is fine on the rods and mains.

Daniel

just measured my crank with a set of calipers, probably not as accurate as a mic , but i got roughly 2.725 on the mains, and 2.185 on the rods, so that would be .02 under correct ? So i need to buy bearings that are .02 under right ?

Do yourself a favor and take it to a machine shop and ask the Machinist to mic them for you so you don't buy the wrong parts! pdq67