Shifter won't move with a rebuilt 727

I know it's not an A body however, I've been on this forum for a few years and I've received some really good advise from many members on here so I figured I'd ask for help with my Trailduster. I have a 75 Plymouth Trailduster sport with the 440/727 combo. I recently rebuilt the transmission as it had completely lost 3rd gear. It was my first trans rebuild and I followed the books and videos throughout every step. The only exception being my 727 is a 4x4 model whereas the book and videos are all 2wd 727s. I have an aftermarket B&M shifter so it's simply the cable connection to the shift linkage. I can't get it to budge. Any ideas?

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Burned cable? Maybe disconnect the cable at the trans to verify the arm moves.