as you can see I haven't dug into this part at ALL.......yet. So in your note above, when you say the 'other half' (of the C500) you mean literally the 'second block' that splits away at the C500 so that ONE 'block' is for ie lighting etc ONLY (note: I am assuming EVERYthing here, not making statements...) and the OTHER 'block' of the C500 is for 'non-engine management etc'.......
Correct.
Identifying which is which is simple--of the two male connectors at C500, one will have a bundle which snakes over to the engine. The other loom
normally loops up and over the upper RH frame rail, between the outside of the frame rail & the rear clip. Hopefully whomever originally installed your body kit followed similar routing.
if so, then where do the ECM 'controls' come in? I expect it must be in there somewhere... for oil pressure/fuel pump linking; ignition control; injector control etc etc..... is that sort of stuff all run thru ONE block (only) of the C500 or is that stuff separate wiring altogether? I have some VERY good wiring diags of the fiero circuitry BUT it doesn't show where the wiring goes thru connectors....
Yup, it's in there somewhere.
The ECM has a direct connection to the injectors, ignition module, MAT & CTS sensors, fuel pump relay, and a few other things I'm probably forgetting.
The main harness carries the signal from the VSS, connects to the fuel pump, oil pressure sending unit, idiot lights, etc.
Yet the ECM needs the VSS signal for some of its work, not to forget ultimately having control over whether or not the fuel pump is running, and directly drives two of the idiot lights.
Under the center console, just below the ECM, there are a couple of flat connectors which link some of the circuits in the main harness with those of the ECM. Power to/from the fuel pump relay's contact goes through there, as do the signals which operat the "shift" and "check wallet" idiot lights, and more that I can't think of at the moment.
Bottom line: I can literally leave 1/2 of the C500 alone; a whole 'block' of it (lighting etc) and only have to use the wiring for the other 'block' or 1/2 of the C500? Seems almost too convenient....
which is why I am asking.
With respect to installing your engine, yes.
With respect to your alluding earlier to having some work to do with your rear lighting, possibly no.