Here is a little food for thought on the SPF replacement rotor situation:
The '89 to '92 T-Bird rear rotors are available from AC Delco at
PartsGeek.com. <= Clickable
The AC Delco 10" diameter rears are $23.99 each.
The '78 to '90 Caprice fronts are also available from AC Delco at
PartsGeek.com. <= Clickable
The AC Delco 12" diameter fronts are $51.99 each.
If you want to spend a little more $ there are drilled and slotted versions available also.
The Delco rotors will require the Wilwood calipers, so if you have a chassis number w/o Wilwoods you have an additional $150 or so to spend per wheel for calipers.
Summit has the front calipers (JL-120-13845) in anodized gray for $150.10 each.
Summit has the rear calipers (JL-120-13840) also in anodized gray, for $150.10 each.
The cost to upgrade from the OEM calipers and limited brake pad choices is relatively low and the ongoing service of the brake system is again quite reasonable.
Something to think about ...
p.s I did not speak to the fact that you will also need caliper brackets to support the Wilwood calipers. A quick search of the Wilwood offerings has prices ranging from about $10 to more than $100, so a visit to Wilwood or Hilbank by phone might be in order so you can more easily identify the correct bracket(s) if you need them.