89 silverado 5.3 swap

so im starting my swap and getting everything ready for the new motor. the motor and tranny are coming out of an 03 tahoe and i have a question. what wires do i keep that run out of the driver side firewall on the 89? and will camaro longtube headers work on this motor and clearence my frame?

id think all youd need is your ALT wiring, ignition to your starter, your oil pressure wires, and temp wires
the fuel pump should be ran off your new harness. i may be wrong i dunno. im just ordering a new harness if i fail at my reworking