What year is the LQ4 that you have in your truck? up to 02 you need to replace the crank/rod assemblies with LQ9's. All 2003 and 2004 model year LQ4 engines had the updated crankshaft but had pressed fit piston pins. The pressed fit pistons are the same weight and mass as a full floating piston. Mixing pressed pin pistons with full floating pistons will not cause a engine imbalance.(assuming you use OE replacement pistons). Dont have alot of info on the LS2 tho.