Ok, here's what I got:
I have a complete wiring harness from an 89 k1500 5.7 TBI, TBI unit, and ECM.
I want to adapt this stuff to my new rock buggy with a Chevy 350 engine.
I would like to set it up similar to a Howell kit, which has only a coolant temp, O2, and MAP sensor.
My questions are:
1. Does any one have a drawing of a Howell harness or similar?
2. Can the harness I have be used sucessfully?
3. The ECM I have is from a 5.7. Will it need a new prom in order to work in this simplified setup?
Thanks.

I don't see why you couldn't use the harness you have, but I'm not too familiar with the howell setup. You will need a new chip for sure. But there is no way you can get around not having a TPS or certain other sensors, at least not with a 7747 ecm as far as I know.

I had the howell kit on my jeep. It uses all the sensors a stock gm tbi setup does but there kit does not control timing it has you use the stock vacuum advance on the distributor. The only thing there harness does is have a convertor init to make the tach signal trigger the computer for injector pulse. But if I were you I would use the distributor from your donor vehicle so you won't need any of that.

I ordered some small parts from Howell and they said exactly what you said.
They said the harness and ECM I have will work if I use the ESC module and spark control distributor and all the original sensors including the knock sensor. They also said their harness has the tach filter which allows the exclusion of the spark control module and distributor.

Does any one know what the tach filter consists of?

Does anyone know what make and year vehicles had the ESC module and distributor?
I have the most access to cars in our bone yards.

Any 87-91 c/k truck should have the distributor and the esc module you should need. Just get it out of a 350 engine application. They are different ones for different size engines I believe.

Trucks are the problem. The yard I go to "pick and Pull" has very few trucks and none in that year. I will probably have better luck finding a car in that year.
Thanks for the help.
Here's my web site.
www.trailhed.com