Hello, can anyone tell me what the modifications are to make a 70 core support work on a 72?

 

It would be a lot of work to modify a 1970 to work on a 1972. You would need to cut and weld portions of the 1972 into the 1970. I think you would be ahead of the game getting the correct 1972 core support for your car.

 

The modifications are:

1. Sell the 1970 core support
2. Buy the correct 1972 core support.

As John notes, if you are trying to fix the typical rusted area under the battery, cut those parts from the repro and weld them into the good parts of the original 1972 core support. It's the top plate and the center latch support pieces that are different and not easily modified from 1970.