I'd do the checks noted above. Then, slap 6 quarts in it with the filter and go. I've yet to see any engine (SBC, BBC, FE, W, C and more ) where filling a stock pan got the oil level, at rest, anywhere near a windage tray. And while running, almost 1/2 (maybe more) will be whipping around the heads, intake valley, etc. futher lowering the pan's level. JMO!