the 4x4 trucks and Broncos from the late 70's used the rear sump oilpan. Also, but rare, the 400 was available in 75-91 vans. Here is an excerpt that I wrote for a newsletter.....for 351C/400 he says that there was a rear sump pan on the 80-82 F150 that is now obsolete. I know there were a few vans with a 400 in them that would have it but I have only seen one. Again, this was a popular option with 75-79 4x4's. Canton makes a dual sump pan to fit in fox-chassis Mustangs. Part numbers #15-720 with #15-721 screen and bolt and #20-850 dipstick kit.
I just swapped a '74 Bronco rear sump for my front sump when I put in the Dakota crossmember kit and IFS (with Rack & Pinion, too) on my '59. I traded the old front sump + $75 for it. Hey, he had me over a barrel, so I took one for the team!!!
Hey thunder, you and I have some things in common here. I got my 400 out of a '71 LTD and it is in my '53 F-100. I had the same problem with the pan conflicting with my volare clip, and wanting the engine lower in the bay. I went to the junk yard and got one from I believe a '78 F150 351M 4x4 with the rear sump. When I ordered my high volume pump from Summit, I also got a new rear pickup from them as well. The setup fit perfect. If I remember right, all told it cost me less than $25 for the used pan and a new pickup, but it's been a while since the purchase.