CH302K.... welcome to the forum.
I would recommend looking at the tach sensor, which is the 1" pipe plug with the 2 wires coming from it on the drivers side (USA) of the IP Gear Housing. It may have a bare wire or two. May even be weeping oil around the wires...
Also, since this is an IDI, this forum is more geared to the PSD's.... I would recommend visiting out sister site
Oilburners.net and post the question in the IDI section over there. Is it probally the best site for the IDI on the internet. These guys know these trucks and engines inside and out...... it is a great site... and you will get your questions answered.....