Install a Tremec T56 Magnum in your A-body

Are all the crossmembers the same? I have an e-body and an a-body. The E has a TKO that I want to replace with a Magnum. My A-body project is getting one too, it's an auto, but I don't know which one is getting the swap first. It would be nice if they were compatible so I could decide later if I buy one now.