Alot of time will go into the lbz swap.
Quick and dirty is strip the wiring harness down to the bare minimum (I suggest starting w/ a van set up) and run a built 4l80e. Efi live can tune out most the unneeded functions. Then you will have a separate harness for most gauges. This is lower power set up but doable. (manual transmission would also fit here)
Next option, hybrid gmt400xgmt800 full truck wiring to keep bcm happy. This might be the toughest.
Stick the gmt800 full interior and chassis harness on your 400 and adapt a couple plugs where necessary.
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