The I-16 we have is the closest possible, and even It's way too advanced. The power and speed on our I-16 is very much improved over the "type 5" that was common during the Spanish Civil war.
To even come CLOSE to pretending to replicate the Spanish Civil War, you'd need to have D3As fighting D3As.
No other planes, save the WW1 planes, are slow enough to come close. Please remember the Spanish Civil War consisted mostly of biplanes fighting biplanes, the majority of late 1920s design.
Here's a good link depicting which planes took part, even if in a limited role:
http://www.zi.ku.dk/personal/drnash/model/spain/did.html
It's not really related to WW2 other than it was a precursor and shaped things to come.
well im not sure about jumping the Gun, the I-16 would be a pretty good stand in as well as the 109E. Given many of our frames from scenarios and Fso's are entirely off its not to harsh to say the I-16 vs 109e/stuka isn't a bad idea.
Look at the Rangoon scenario - we had A6m5's as Ki-43s and 110C's as Ki-45s, true the I-16 is a little overpowered for a condor legion scenario, its
still overpowered by the 109E's. I would say arm the I-16s with ShKAS machine guns and it would be a pretty good match up.
Much as I would like to see a condor scenario, the plane sets are to far off to be a historical scenario, I really don't like the idea of swapping out historical aircraft with "others".