According to GM Heritage, the original 17" wheel is 5" wide. I take it you have the original multi piece wheels? If so, you may find some difficulty finding anyone willing to service them, as it's obsolete technology. Most tire shops simply aren't setup for that type wheel, and aren't willing to equip or train for them. You really should also run the proper type tires for them, either bias or tube type radials. Tubes in tubeless tires is not recommended by any tire manufacturer, and the manufacturer warrantee will be voided.
