My truck is an 89 K1500. I swapped out the gauges affectionately know as "moonies" (88-91) for a set of needle style guages found in 92-94 Chevy 1500 style trucks. This necessitated swapping in a drac module to run them. My drac currently runs the ECM, cruise, RABS and speedo. My truck has the 40 tooth reluctor ring on a 700r4. As my drac is a 93 for the needle gauges, it's putting out 40 Pulses per driveshaft revolution vice 2000PPM which is what my current 1989 7747 is looking for. Runs fine in both mileage and driveability aspects. My question is will the 93 drac run the 85-89 MAF setup I recently bought (well, hardware is 87, harness and ecm are 1985), which is also looking for a 2000 PPM signal? I think there's been a couple tpi swaps done by gents frequenting this board on 93-94 trucks. I'm looking for their input on what they ran into (or anyone else who knows). The harness on the way has a 6870 (1985 MAF), which I will probably switch to a 7165 with a little "re-pinning" because of the 6870's abysmal low BAUD rate. Meh, maybe I'll just switch to a 7730, go speed density and be done with it...if it will work with a 40 PPr Drac that is.... Now where did I put those wiring diagrams again? ;-)

this will probably get locked soon because its not really thirdgen related.

the 85 computer system is the worst of all the TPI systems, not so much because of the slow BAUD rate, but the MAF sensors on them were junk when they were new systems. then there is the MAF burnoff relay that was used on that system.
so i would without a doubt use one of the other ECMs.

i don't know if the 165 will accept the input from a DRAC from a pickup or not. i would guess it will because the 165 also used a DRAC.
if it does, it may need to have a constant changed which will require you to burn a new chip.

to use a DRAC on the 7730 ECM will require chip tuning.
the 40 pulse per revolution speed sensor signal is too fast for the 7730 ECM to properly use as an input even with chip tuning. at least i think its too fast.
depending on the rear gear and tire size, above a certain speed the ECM will start to show a slower speed than what the vehicle is actually going. the faster you go, the slower the reading gets.
so a DRAC is needed.
on the 7730 system, in the bin there is a switch you can change so the ECM will recognize the DRAC input. then there is a constant that may or may not need to be changed so the ECM will see the right vehicle speed.

if this does get locked, you may find some more info that your looking for over on full size chevy.

Unfortunately I do believe you would get better results from a truck forum about your gauge setup. You should try www.gmfullsize.com, www.fullsizechevy.com etc. I typacly leave threads open that have problems dealing with TPI related problems in general, this to me seems like it is a dash cluster problem for a truck which is out of the realm of the thirdgen f-body so I will have to lock this. Please PM me if you have any further questions to why I locked this.