If you have the money ($950+) I say go for the Nelson harness. But if you want to try and save money, you can find a junkyard harness and have it modified or take the time and research how to modify it yourself. Either way you're going to have a standalone harness with minimal connections to plug into the body. As far as the trans, I would personally find a 4L65E or 4L80E, cuz even a rebuilt 60 probably wouldn't last you too long especially after modifications.