I'm out of my wheelhouse here, but I'll tell you what I've read here and on the P'up site.
There is very little parts support these days, and almost nothing on the aftermarket that is specific for these trucks.
For the front, you can get a bit of lift by re-indexing the torsion bars. But not a lot. To go higher, you may need to do a solid axle conversion.
For the rear, there are shackles. An extreme driveshaft angle will accelerate u-joint wear.
Jack
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'83 Isuzu P'up Diesel LS - Original Owner
JoeIsuzu@IsuzuPup.comIsuzuPup.com