Wiring Help

Thanks for letting me ask. If I’m in the wrong place let me know. I took a 1997 Chevy Tahoe 65k, 5.7, 4x4 and took the body off. Didn’t cut ant wires. Unplugged 3 connector from the firewall and removed body. Engine and frame is still wired. Sent the ECM off and had a mild tune, back o2’s off and theft. My question is do I cut the cab side Of the wiring plug off and hook my new power to it or cut the entire connector off? How do I keep the OBD port and the check engine light. Does anyone have a wiring diagram. Have several and they all say different. Thank you for any help.

\sorry i dont understand the question really why do you need to cut any wires at all ?