All sorted out and ready to revisit the NeXTretro schematic!

The figure from the 68060 manual has a few typos, which I have corrected.

The signal updates are justified by:
TTx: 68060 Section 2.3.1, three state signals
/TA: 68060 Section 2.5.1, /TA is an input; whereas on the 68040 (sec 5.4.3) , it is tri-state, bidirectional signal

Excluding the clock, and power, here's what has to happen to make the 68060 act like a 68040.
1) /SNOOP held high, to mimic the SCx wiring on the 040.
2) /CLA is held high.
3) /BTT is held high so that the 060 acts as an 040.
4) /IPLx is held high so that there are no interrupts.
5) /AVEC is held high and disabled.
6) /TRA is GND and asserted for 040-style bus termination.

Excluding the address and data lines, the total are as follows:
input: 13
output: 9
bi-directional: 4

The 040 on the NeXT does not use the /TIP signal, but I will use that for my bus mux logic with the /TA signal. I will have a pull-up to /BB and use /BB and /BG to drive my outputs (060 section 2.7.2)

It looks like I am ready to revisit the schematics.