> We used the (CMOS) 74FCT623 because it is easier to
> get than the ABT part. (ABT is really top-of-the-line but the FCT
> will run even cooler.)

Am I parsing this correctly: you are saying that the FCT part generates
less heat than the ABT?

I've found spec sheets for the stock Signetics F part and a TI ABT part.
The ABT part should generate a lot less heat than the F, and is rated
to survive higher temperatures than the F.

The TI ABT part number in the package (*) we need is SN74ABT623DW

* SO ("Small Outline") 7.5mm (0.3") body width, 1.27mm (0.05") lead spacing

-Dave