E body bucket seat core frame interchange?

Is the 1970 cuda bucket seat core frame the same as on a 1970 Challenger with bucket seats?

Yes, but be sure they are 1970 frames. I have seen some 71 style frames that people have put the 1970 upholstery on.

Make sure that the backs have the 1970 style release button.

From what I have seen, the seat styles between 70, and 71 was changed mid year of the 71 model, I think in December.

What is the difference between 70 and 71 seats? Does the 71 have the foam backrest instead of springs like the 72 and up?

The latch changed. The 1971 style has a box welded to the side for the newer style button & retainer.

The spring style was used from 1970 into some point in the 1972 model year.

Thank you.