I don't have the paper with me that came with 'em offhand to give you the exact model number, but I bought them from an eBay listing, this being the model and price:
http://cgi.ebay.com/ebaymotors/Q-Log...sid=p1638.m118
The model for my truck is a slightly different number if I recall, and if you buy from Q-Logic they're $150+. Being the eBay hawk I am, I took a gamble with the Blazer ones since I figured the cab dimensions would have been identical for those years (my truck is a 1973), and it worked.
My component speakers were 6 1/2" though, and wouldn't fit in there properly like the right set of component speakers would. So I took a piece of garden hose, wrapped it around the inside of the enclosure (yet with a hole cut big enough in the speaker blanks for the speakers to squeak through), and screwed it into that. Worked like a charm, provides a nice cushion/absorbing effect, too.
So if you go the garden hose route, you
could fit the 6 1/2" in those with a little craftwork. Since the new 6 1/2" Q-Logic panels cost around $150, and I'm not sure if they've made the bigger ones for all years and makes yet.