I remember the wire colors from the seat not matching up with the colors from the floor, and they might have even been different seat to seat. I think I spliced them up according to which wire they connected to from the floor - everything worked OK.
I didn't sweat removing the connector off the original seat BC they were going back to the salvage yard as a core, and they were in really bad shape anyway.
I've never messed with disassembling harnesses, that is probably a good option. Worst case you could use bullet connectors instead of a butt splice - then if you want to use your old seats again could easily swap them out.