OT there might be a slight difference in the fore/aft spacing of the DR block ears & possibly a difference in the space between the block ears on that same side so check that out & some spacers/washers will take care of that as needed. there are (2) "center sump" 360 pans that I am aware of, the sump(s) ain't exactly center (are more toward the front) but are referred to CS pans as opposed to front "van" or rear "truck" sump pans. On the "392" the sump starts ~4" from a line vertical plumb down from the very front pan lip and on the "876" pan the sump starts ~2". both sumps are ~8" long & they take different oil pickups. visual on your 340 sump/compare it to what you have on the 360 to see if you will be in the clear. Having the eng "almost" dropped all in is definitely not the time to have an issue there!. As said keep the 360 dampener as is up front & do what you need to do to keep the rear part of the external 360 balance on the 360 as it needs to be.