Yes, you need to change transfer cases. Manual trans xfer case uses a 10 spline input and a th350 uses a 27 spline. You could just swap the shafts but you have to take the whole thing apart to do it.
I don't think you have to swap the crossmember just move it back.
'71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
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