Your engine will be just fine for a very long time. the Mitsubishi Forklift 4G64 motors, come from the factory without balance shafts.
I've been racing mine without Balance shafts Since 2004. Balance shafts are for your butt, not the engine.

Just about everyone who re-builds a 4G6X motor drops the balance shafts, less to break, its a real bummer to break a balance shaft belt and have it destroy the CAM belt and valve train. One of the main reasons for the Balance shaft delete.