440 pushrod length

Having trouble determining the correct pushrod length for my 440 R/B. It's a '72 HP block with 906 heads, an Isky .505 lift cam, hydraulic lifters and Harlan Sharp roller rockers. Problem seems to be that the oil hole on rockers requires the cup end to positioned so that oil gets into the cup. can anyone help???

Any time your using aftermarket rockers, an aftermarket camshaft, hopefully milled heads and/or decked block you need to measure for correct fitting pushrods... Typically this is done with the engine mocked up, cam on the base circle, headgaskets in place, heads held by a couple bolts, rockers bolted down, adjusters centered in the oil groove, use an adjustable pushrod to measure he distance from the point of the adjuster where the pushrod normally contacts to the pushrod cup in the lifter without depressing the cup at all, with a hydraulic lifter you want to add .030 to the measurement for lifter preload..