For those keeping score at home, I sent a message to SGA last night, asking about either tranny, and would I need a tuning device to install, in addition to the SGA harness? He wrote back that either tranny (870RE or 8HP70) would work (he has not seen one that didn't), and I would only need HPTuners if I wanted to change the shift points for the transmission. He said that could be needed, as there were no 4.7Ls produced with an 8HP70. He recommended I get a tranny from a RAM 1500, which is what I was thinking.