Thanks for the info. It's a huge help having the frame model narrowed down. The A-body / G-body makes sense, since the 1990 S10 seems to have used the same upper control arms as the 80's Monte Carlo.
(example: right upper control arm Alternate/OEM Part Number(s): 12376266, 12543948, 19133654) source: rockauto.com
I also found this FAQ about the 1978-1988 A & G-Body Chassis Information, including what parts are interchangeable between the two.
G-Body Chassis Information