First Gen Blazers (rounded body) from 69-72
Second Gen Full Top Convertible (squared body) 73-75
Second Gen Half Top Convertible (76+)
That blue 73 has been for sale in seattle for a while now. I'm guessing you could talk them down in price. It looks to me like the driver's side has been hit at some point (missing the trim, etc.). I'd look hard at the repair job to make sure it doesn't have bondo (trim holes are filled).
I've seen a few really nice 73-75s for sale around here in the past. They don't demand as much as the first generations but more than the half-top versions.
Here's a 2wd in Portland with a funny paint job -
http://seattle.craigslist.org/see/cto/2198116315.html
They do look nice with late model front clips. I've seen a few late model trucks converted to full top convertibles using the top and windshield frame from a 73-75.