The only thing the 4T60 needs from a computer is a signal to lock the TCC... other than that it's still cable and vacuum controlled. So yes, it could work with a stock Fiero automatic ECM, but requires adapting the VSS signal and inverting the TCC signal (the TCC works differently in the 4T60 than it does in the 125C).
is a bit more involved with an '88 because the location for the rear trans mount slopes up differently where normally another slotted hole is made on the pre-88 cradle...
This is what has kept me from looking at the 4T60 swap over the years (especially when I really wanted a manual anyway).
[This message has been edited by carbon (edited 04-11-2016).]