30-31 vs 40-48 Clamshells

[klawockvet]

I have an early AR 6 bolt clamshell and inner u-joint cover and am trying to install an F150 trans. I need a later style 4 bolt cover and clamshell and have one on a 40 that I could use but it will be a bear to get it out. Will they interchange or do I need to find a 30-31? I would much prefer to just buy another one if I could get it on the west coast as I'm running low on time to get the car back on the road.