don't know nuttin about 427 motors, but when i need to drop the sump pan on my Windsor, it hits something at the rear, it wouldn't drop off the bottom of the motor. So found out i needed to loosen the bolts holding the bellhousing to the motor, just a quarter inch, pry it back, (loosening the transmission rear bolts too), then the pan would drop right off. No need to mess with the front cover at all. I also found it tended to hang up on the
oil pick-up with the baffelling in the sump, took some wiggling to get it to drop away.
Anyway, for me, it was a ten minute job to pull the bellhousing back ever so slightly. Used a bar lever at the rear of the transmission with a wooden block to lever it back. Easy as pie.