71-72 vs 73-74 B-body Rear Frame Differences?

I have an Auto Rust Technicians fabricated rear frame cap that was designed to fit over the left side rear frame (under the trunk floor)of a 71-72 B-body. In the end it was not needed for my 71 Road Runner project. My question is how similar are the rear frames on the 71-72 & 73-74 B-bodies, and if my existing cap could be used on a 74 B-body.

I asked Auto Rust Technicians this question and they do not know.

Anyone know if this would work or how much my cap would have to be modified to fit a 74 Charger?

I could be wrong but I don't think they really changed the car structurally from 71-74.

71/4 are pretty much the same frame rails.

Thanx Guys!