I want to buy an electric fan for my 84 firebird i've got a mechanical one and i was looking to get a permacool one thats 16" 2100 cfm draws like 9 amps i think but my question is that going to keep my mildly modded 305 cool? can i go to a smaller fan that flows less and still be ok with temps? i want to run a switch that i can turn it on/off do i run a power wire to the switch then from the switch to the fan and ground both?

I would use the 16. You will need a relay in conjunction with the switch. 9 amps is more than a garden variety switch can handle without getting very hot and failing. If you are going the electric route I would still use some sort of automatic control, it's too easy to forget if you stop and shoot the bull with someone when it's ideling. If I were you I would look for a dual fan setup, one automatic and one on demand fan would work well for you.

I run a dual electric fan setup from flex-lite with a 3 row radiator.It comes with a thermostat so you can adjust when you want the fans to come on.I run a 160 thermostat.Its worked well.