If you can physically fit a CS130 or an AD230 (CS144, AD237/AD244 if an HD charge with a larger spacing for the ears, but i dont think yours has that from the looks of it) which are common retrofits onto small blocks, big blocks, and I imagine wouldnt be too hard on a diesel(Im unfamiliar with the amount of room, bracketry). If you can put one of those on, you will increase your alternator output a good amount with a very good upgrade to the features including a built in tachometer signal on the 4 pin plug, the only other wires relevant also being on the same plug(one is a sense wire like yours has I think?) and one is to a charge light or resistor for turning on like yours would also have.
Im not sure how those signals work or what all goes into it, but i Believe its similar to a HEI tach signal unless IM mistaken.
Just a thought if you would like to upgrade your amps too. The cs130/ad230 alts also have built in delays that soften the sudden load on the belt as well which could reduce any possible slipping with large demand or wear on the belts, since the old ones are more ON/OFF and that can shorten a life of a belt especially when its not dampened with a tensioner like a serpentine setup. if you wanted another benefit
