Merging wire harness is very challenging!

I've worked with several L31 conversions on the 1986 - 1995 pickups, re-using all the original TBI harness.

For 1986 - 1992 an upgrade to the 16197427 PCM is required.

The next step is to convert the 16197427 computer to MPFI, which mostly consists of rewiring to the L31 injector pod wiring to the TBI injector wiring.

The next wiring modification is to add the 4L60E wiring harness.

Then install a custom PROM chip, and tune as required.

dave w