After 255,000 mi. my pulley bearing finally wore out on my '94 Safari, 4.3L TBI. I tried NAPA for a replacement but was referred to Chevy. Chevy lists the pulley as being part of an assembly (the casting that the alternator & tensioner mount on) which sells for $113. The guy at the parts counter felt bad charging so much so he cut me a break & only charged $90 which was cool but I still have a large, over-priced casting that I'll probably never use. I didn't think to look at this bearing until I'd already bought the new pulley. The bearing # is 6203 LH. A dirt common $7 part from Grainger (which is like the 7-11 of industrial/commercial parts houses) & easily pressed out and replaced. This turned out to be an expensive lesson with something that I should have known better. I don't know yet what # the tensioner bearing is but I believe it ( the assy.) goes for about $65. I'll be paying a little closer attention next time.

Thanks for the info!