It's a good idea and a great head start, but as I said I wouldn't bother with the stock ECM and for that matter, most of the harness. Keep the wiring pigtails for the sensors and the injectors, obviously, but there's probably a lot of the harness you won't need or will need to modify in order to fit and function on a long inline rather than a stubby V6. The GM ECM requires a specific set of sensor inputs (such as crankshaft position) that you may not be able to easily duplicate on the 170. Spending a few bucks on something like the MegaSquirt will ultimately save you time and money over trying to make the GM computer still think it's attached to a GM engine. Something as simple as a firing-order difference will completely screw up the GM ignition and injector timing, which is not easily overcome with a waste-fire DIS ignition, which I believe that Celebrity used. Even with a distributor, the archaic computer controls the firing.
Once again, I'd suggest you hop over to DIYAutoTune's website and/or the MSEFI forums and ask. MPFI Slant Sixes have been done time and again, but probably not with the stock GM computer. All those sensors, injectors, etc. you have can still be used with the MS system, which comes already set up for many GM sensors but can be programmed for almost anything. Plus, chances are there are folks out there with base fuel maps that could get you up and running quite nicely with a stock Mopar ignition (even points, if you're retro). Once you've got the fueling in place, you could then concentrate on something more exotic in the ignition department... and unlike using the GM computer, you'd have full control over air/fuel ratios (and if you choose, spark) which you could maximize for economy. That's something the original ECM was never designed to do and can't be talked into doing, either.
Time is money. It's your call how much of either you're willing to spend trying to make the system work as-is. You'll likely wind up with a minimal improvement over a well-tuned OE carburetor/electronic ignition setup should you decide to stick with the GM computer. Technology is leaps and bounds past the giant DIP-package PROM chips, KHz processors and narrowband O2 sensors of 1986. Make use of that, and as a bonus you'll learn quite a lot about EFI on the way.