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).
The
swap 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...
Pre-88

1988


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).]