1988 GMC C3500 Dually 5.3 4L60E Swap

[BRANCOTRANSPORT]

I was hoping someone could help me with any info pertaining to the wiring of my 5.3 into my 1988 GMC C3500 which was factory equipped with a TBI 454. My donor vehicle is a 2002 Chevy Tahoe. Questions include how much of the existing harness may be removed and still retain complete instrument panel function? I'm very new to LS swaps but a very competent mechanic and 12v electrician. If anyone can shed insight to help me expedite my swap if appreciate any and all info!

[1991SSP]

I did the 5.3 swap on my 1994 model that had a V6 in it.. I went with a stand alone harness from nelson.. I ran the wires from their harness for the speedometer/tach/check engine light thru my firewall and directly to the plug for the cluster, as the cluster I had a pinout diagram and clipped the wires and soldered the wires from the nelson harness them in their appropriate places.. as far as water temp and oil temp you will need adapters to use your sensors from the 454 on the newer 5.3 engine, I did this as well,,, as far as the factory harness I clipped off all the plugs that were not needed,, taped them up and stuck them back into the factory wiring loom... that way I could re use all of the wiring for the factory AC....