I have trouble with my 5.9 Magnum using the factory timing cover dipstick with a mid-sump pan. I had to pound down the front pan baffle a bit so the stick would side back there easier. I also had to have an extension tigged onto the Milodon dipstick so it would reach. I keep a longer factory style dipstick in the trunk so I can see the clean oil easier. It's almost impossible to see on the small round wire that comes with the Milodon stick.
It sounds like you may have to use a truck type dipstick. I believe they came with rear sumps.