For the Vortec motor, it is internal balanced but who cares? Go to the Chevy dealer (dont wear any Ford shirts) and ask for a manual flywheel for that engine (98 Vortec). There will only be one that fits, you will not be given a choice of a 153 or 168 tooth wheel. The one piece main engines have a bigger bolt pattern than does an earlier small block so the choice is what it is.

Get the bolts from the Chevy house also. You will have to get a clutch pressure plate to match the flywheel pattern and a clutch disk with the right spline for the tranny. Vortech engines had a hydraulic clutch and would simplify your linkage but cause you to put in a clutch master cylinder.

Have you ever driven a bucket with a stick shift? Make sure you have a washable interior in the thing.......