Ok, first off that pic you posted of a shunt is from an A0 schematic... as far as I am aware they did not use one on the A1's... a shunt is used to measure current flow, and on the A0 it was in the ground path. Its output only fed the STE test plug...
Battery ground should go direct to starter motor housing, with a braided strap connecting it to drivers frame rail.
Batt +12 goes thru manual disconect, remote disconect and to LBCD 12v battery terminal. Alternator 12v cable is also connected there.
Batt +24v goes thru manual and rem dusconnects and to 24v batt terminsl.on lbcd, 24v alt is connevted there also.
The 12 and 24v load terminals on the lbcd feed to.the cab...