I am still trying to get my rear axle fixed, and of course we just got 7 inches of snow today, and no truck. But anyway back to the question the rear drive shaft is shot, i am either gonna replace the factory 10 bolt or go to 12 bolt depending on availablity, my question is this, every place i try to check on it asks which spline count i have (20 or 28 cant remember the number) or a 30 spline. which is the factory option-i have the overdrive auto on my 88. also will i need anything different if i go to the 12 bolt as long as i stay later model chevy. ( i.e. new driveshaft or different ujoints on one end.) Sorry to ask questions but i could not find answer on searches. if someone could help me or tell if there is a factory sheet somewhere on the rig that has theose codes i would app it.