I would not wast the time on a 88-91 TBI; the last one I had ran good but MPG? in town empty? 8 MPG. on the road empty? 10.5MPG. in town towing? and/or loaded bed? 8 MPG. Empty 70MPH down the interstate, no T gate, 35 MPH tailwind? a whopping 12MPG. this was an 88 D 100, 2WD shortbed, 318.
the current 88-91 TBI albatross in the garage: 89 RC 360, my son's, recently bought; cannot get the TBI to run correctly to save my life. My solution? It's getting a ThermoQuad! Screw the TBI!