i had an 86.5 (hardbody) nissan v6 pickup, tough little b*std that went everywhere without a problem.
the old 720's (like yours) have no aftermarket really. the hardbody's (around till the frontier came out) have a pretty good aftermarket now, calmini is the main place to get parts from.
720's have that odd t-case setup which robs ground clearance like crazy, the hardbody's (86.5-97) are a driver side drop with around a 2.3:1 low range if i remember right. will go anywhere an ifs toyota will. nissan engines (of the hardbody era) has slightly more power than toyota engines of the same size, but the trucks also weigh more. the 4 cyl axles arent the best, but the v6 h233b rear axle is extremely sturdy.