CP,
My book says 3965577 is from 70 Corvette, Camaro, 4 BC, cast iron, 300 & 350 HP.
The closest to the other one is 340281 - 305,350 82-85 pass. or Camaro cast iron Q-jet.
or 340261 - 340261 350 74-76 pass., Camaro, Chevelle, Nova.
I think the first one lends to higher performance. Just my opinnion.
Hyperman
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Miramichi,New Brunswick
Canada
http://personal.nbnet.nb.ca/petako/Graphics/hyperman's%20chevy.htm
68 Chev short step 2wd (Ground up resto in progress)
69 Chev SWB 2wd (parts)