Check out this site. It lists all Toyotas by body # prefixes like KZN, LN, ect. JDM frame numbers are not like US vins. The long number after the model tells when the vehicle was built in numerical order.
(edit)Your Truck was built in March of 1990
I assume you're talking about the 2L-TE head that goes with the data plate? No, it's never had any problems in almost two years of use and several trips to Canada, one towing a portable sawmill. The current owner did manage to burn out the flywheel pulling logs off the beach though.