I have successfully installed Mopar Performance headers today in a 78 Dodge d150 with a bell housing and A 833 out of a early A body(high mount starter). It became obvious early on that they were not made to clear the truck oil pan so I got a hammer and then a really big hammer and made a 1 1/4" deep indent up the side of the oil pan sump, there is a steel brace between the block and bellhousing that needs a big notch cut out of it and a redundant corner of the bell housing needs to be lopped off. Other than that they cleared the frame nicely, cleared all linkages. one warning the angle of the collector was not true to run a pipe fore and aft and I diden't like the loose flange arrangement so I did a mock up before hand and welded fixed flanges to 3" pipe. Got a Dyna max 6" diameter glass pack 3" in and out and a Supertrapp 5" disk only on the end to tune back pressure, figure if I take out the disks I'll be really close to open headers. Can't wait to here how it sounds.
Bruce Johnson