There may be more authoritative sources, but, according to John Gunnel's 1987 book,
Chevrolet Pickups 1946-1972, here are the numbers...
1970 C-5 (2WD) Blazer: 985 produced selling at $2,385 each
1971 C-5 Blazer: 1,277 produced at $2,659 each
1972 C-5 Blazer (6 cylinder): 487 produced at $2,585; C-5 Blazer (V8): 2,870 produced at $2,700 each
Don't know the GMC Jimmy numbers. Evidently, much of the marque's historical data was lost in a fire or some sort of catastrophe. LUV2XCLR8 started an informal database over on the Chevy & GMC Int'l Truck Club board. He can probably provide an update on its current status:
http://www.chevygmcclub.com/vboard/showthread.php?t=380.
I'm sure others can add data and fill in the blanks.