Update on my progress, installing the 1987-88 EVIC in the 1993 Daytona:
I removed the compartment below the radio, carved the plastic trim edges of the EVIC with a Dremel tool to get it to fit in the cavity, and rigged the existing screws to hold it, albeit at an angle. I tapped into the 12V batt, ignition and ground that runs my fire scanner as well as the car radio, and the EVIC does power up and display the correct day, date and time, and elapsed time. It still shows zero mpg instantaneous and average, as well as distance, because I ran out of time/daylight yesterday. I rigged signal wires from the EVIC which I have to splice to the speed sensor and fuel gauge wires at the BCM, a simple task that will take no more than 1/2 hour.
As for the fuel injector signal, as I said before, it is at the logic module in my 1984, but not at the BCM for my 1993 (because the 1993 had a serial bus that carried the injector data). So I'll have to rig a signal off the fuel injector somehow. In the 1984, I was puzzled that when I put a scope on the EFI signal, it showed an amplitude of only 0.4V, which seems impossible. I'm thinking now that I should have unplugged the signal wire from the EVIC and then probed it with a scope, that the EVIC and scope loads together dragged it down. So I'll recheck the 1984 signal and see what I get. Meantime, I expect that when I connect the speed sensor and fuel gauge, I'll get an average mpg reading.
For mechanical mounting, I have scrap plastic strips that I cut out of one of the console compartments, that I'll custom-cut and drill, and glue with epoxy, to make proper mounting tabs so that the EVIC will line up properly in the console stack. This could take about a week, will post pictures when done.