The truck is a 1989, the Z-24 engine was a total GAFF on Nissans part and the engine was only used for a few years in 6000# Capacity and Larger Cushion and Pneumatic trucks.

It is the SAME engine that was used in Nissan Pick Up trucks and marked as the "Nap-Z" engine which had 2 spark plugs per cylinder, if you look at the Cyl head in the forklift you can see the spot where the extra plugs would have gone.

The heads have a tendancy to Crack through the exhaust ports a GOOD machine shop can rebuild the head, and the parts (Head and Block Parts) are common via the automotive aftermarket, again a GOOD machine shop is your key if you want to rebuild the engine.

Tough to put an actual price on the job but I cant imagine the job going through here for under $5,000.

Any Nissan with a model number STARTING with RG or CRG would have the same engine be it Cushion or Pneumatic 6-8000 # capacity if you want to try to find a good used engine or buildable core if yours is not rebuildable.

The Z-24 was ultimatly replaced with the H-25 engine however I am not positive that that would be a bolt in replacement for the Z-24

Good Luck
Scoot (20+ Year Nissan Dealer)