you wont improve or hurt anything doing that. it has an anti knock sensor and the ecu will retard it back (dynamically anyway). just get worse performance and mileage.
assuming the cams/crank is indexed & vacuum hoses are correct, you know you have to jump connectors to set timing?
pg. 14 (EG2-25) (valve adjust/shim info also)
http://www.ncttora.com/fsm/1990-1995...eme/tuneup.pdf
valves shimmed correctly after valve job?
lot of things to check after this kind of a job. too many to list here.
so, here's an engine trouble shooting table for your truck,
http://www.ncttora.com/fsm/1993/engine/63troubles.pdf