More Gen 3 questions

I think the main issue there is just knowing what plug each computer uses. If the XV/S&P computer is just a stock ECM that's had some programming changed I'd think you might be able to reuse the crate motor harness, but you'd have a lot of extra plugs you'd either want to cut off or tape away (injectors mainly). You'd really probably just have to ask XV/S&P if you can to see what computer they use. There's probably also a decent chance the crate ECM isn't a stock computer, but rather something Mopar developed specific for the crate motor just to be a pain in the *** (because I'm sure there's one wire different somewhere...).

As far as accessory delete stuff, don't waste your money on a fancy delete pulley if you don't have to. I can't vouch for a 6.1 without seeing it, but I know on my truck front cover 5.7 I just got creative. I bought a standard plastic idler pulley (like what is found on the tensioner), and made a spacer from some washers to get it in line with the belt and bolted it to a spare hole on the cover. Then just used a string to measure for length and went to the part store to get a belt. Took two tries to get the right length and tension, but it was easy enough and only cost $20 for pulley as opposed to the $100+ for a "delete kit".