I don't know about the 93-99 belts working in your truck, but you can check this website for replacement belts. I know guys who restored their old vehicles and liked their belts - but they can be pricey.
http://ssnake-oyl.com/
LMC and Classic Parts have the belts also. If you can get the GM part numbers for your belts I think it would be worth a look on oehq.com, oewarehouse.com, autopartstomorrow.com, and GMpartsdirect.com. Or, just do a google search for the part numbers.