I don't know if the flared sump on 7 qt. Milodon big block pans will cause the same problems, but on their 7 qt small block pans a little "V" has to be cut out of the K-frame lip to help the right-front corner of the pan to clear during R&R. Also, most small block headers won't work on the passenger side, again, because of the flared sump. TTI & Dougs clear. I think there was one other particular Hooker or Hedman, but I don't recall the brand or #.
Gotta watch speed bumps, edge of pavement drop offs & wheelstands. The extra weight of a big block will be less forgiving.
I believe OEM style Hemi pans are 6qt but not sure about the fit and Steffs has a 6 qt, but it's very expensive.