The oil pan has nothing to do with it, full is full. You would still be measuring the same depth (top of stick down to the full mark) as if the engine had a conventional pan (assuming yours doesn't). With a deeper pan, more oil is stored below the dipstick. Your imaginary full point in relation to the block/crank, etc. is still the same. See if you can grab the casting numbers off the bellhousing flange of the block to determine which engine that is based off of, and get the dipstick for that application.