OK, now this is getting interesting jerz. The engine the P6500 dipstick came out of is an L-28 with F54 block and dished pistons. It had been freshly re-built by a well known local engine builder. When I got the engine it had a P79 head, leading me to believe it did in fact come out of a 280ZX. If that's true, then your information on the P6500 dipstick is probably correct. I measured the dipstick tubes on both my engines. The one on the L-24 is exactly 3" long. The one on the L-28 is 3 1/8." The difference in the two dipsticks, to show full, is 1/4." At this point, I'll be swapping the L-24 dipstick out, and the L-28 one back in. Tomorrow I will carefully measure how much oil it takes to raise the oil level in the engine by 1/4" on the P6500 dipstick to determine how much difference it might make running an incorrect dipstick. I'll let you know what I learn.