I'm back! And with another no-start condition!
Pulled the starter motor so I could squeeze my hand in to try and JB Weld patch a freeze plug on the driver side - that seems to have worked.
After reinstalling the starter, truck turned over no problem, parked, drove, parked. Now - popping #24

• Disconnected starter power + and signal (smaller red wire), still pops
• Disconnected signal wire to starter solenoid/relay, still pops

I believe this tells me there's a short between ignition cylinder --- clutch pedal position switch --- relay? Are there any computer management devices in between?
What wires can I test for the clutch switch?

 

You can use the rubber expansion plugs to replace any "freeze plugs"(core plugs), just FYI, much easier to install

Ignition switch-----Fuse 24------(red/blue wire)--------clutch switch-----(pink wire)----|||------(red/blue wire)------------------------starter relay

||| is firewall connector

1997 had a Factory alarm option, so added a starter disable relay
If you see a white/pink wire at the clutch switch instead of the red/blue wire then you have that anti-theft system in your 1997

Unplug the clutch switch, and see if fuse blows with key in START
There are 3 switches inside the clutch switch, each has 2 wires if used, not all 3 are used in every year
The 2 wires at one end are for starter and fuse 24
One will be Pink, out to engine bay
The other one will be red/blue, no anti-theft, or white/pink with anti-theft, in from fuse 24

 

Good call on the rubber expansion plugs, going to look into that for the passenger side ones.. motor mount seems like a PITA.
Also getting another coolant leak from what looks like the rear of the driver head/intake manifold... gotta chase that down.

So it looks like no anti-theft system in the 1997, 4 wires:

• blue w/ yellow
• gray w/ red - muti-meter reads ground continuity
• pink - muti-meter reads ground continuity
• red w/ blue

No fuse #24 blow with clutch s/w unplugged and key to START.
Perhaps clutch switch?

 

There is no Ground in the clutch switch, so most likely not the issue

Unplug the red/blue wire at Starter Relay on inner fender, that's the Pink wire at clutch switch

Test the Pink wire at clutch switch with OHM Meter, to ground
0 ohms means that wire is shorted to a ground some where, run a new wire from clutch switch to starter relay, finding that short in the harness would take a long long time
OR
Put a jumper wire between Pink and Red/blue wires on the unplugged connector and try to start, if fuse blows then pink-red/blue wire has a short to ground


You already said the fuse blows with red/blue wire unplugged at starter relay
Starter relay is the more common short point, but have taken that off the table since you already tested that

 

You nailed it, yet again. Thanks RonD.
Ohm'd out to almost 0, didn't even bother trying to chase. Cut the pink, butt connected to a jumper wire and connected that straight to the solenoid and she starts. Then went through the effort of punching through the firewall and routing it clean. Capped both ends of the pink and we're good again!
Now to chase down more coolant leaks..