Calibrating a dipstick on a 351C

[WHTNUKL]

I have a 351C with a dipstick with 2 marks on it. I put it next to what I thought was a "calibrated" dipstick and the lower mark (away from the handle) lined up pretty close. The upper mark appears to be put there by someone specifically for this engine. The question comes when I put in a 1/2 quart more than the "calibrated" mark, yet the oil pressure goes to "0" for a second when braking hard at low revs.

I plan on removing the oil pan and putting in one with baffles and windage tray, but would like to calibrate the dipstick while the pan's off. Ideas?

------------------
White knuckle rides require an "E" ticket, please.