Hi, I´m currently looking at a maybe similar setup.
I also have a 1989 single fan TBI camaro in which the fan died.
I fitted a single 14" SPAL fan and a second 10" SPAL fan on the driver side.
I hooked up the 14" fan to the stock fan connector which makes it run when te engine exceeds 235 and/or when switching the airco on.
I found out however that the fan does not run when the engine is off, even if te temperature is still above 220 degrees.
Since I´m not quite happy with this (the stock temperature setup) I decided to get a new temperature sensor.
I could either go for, and this is the part which is undecided as of yet, the solution of repacing the stock temp sensor and get a set that wires up both fans over a non-stock relay
The other alternative is to use the stock sensor (basically use your original fan plus and minus to wire u one fa) and wire up the second fan with
This will allow you to set different temperatures for both the fans allowing for more tweakability athough I´m not sure if it would be a technical benefit compared to the first alternative.
Personally I do not like the stock setup rewired to fit two fans.
I hope all this applies to your situation and is of some help. Personally I´m undecided as of yet and currently do no have the funds to try both