By the number of read/replies, you can see that cooling is a very familiar topic to most C3 owners.
Re-read the thread and follow all the advises (they were all excellent) especially concerning little things at first (coolant level & mix, bottom hose spring, top seal, thermostat, radiator cap, visual inspection of inside radiator, timing,...) Once all those "cheap" inspections are done (and/or fixed) see if you still have the problem (and 200 is not that bad, so don't rush into huge expenses; find all the small stuff first).
If you still do have a heat problem after all that, then you can start thinking about bigger things (more expensive...) like the radiator (aluminun rad. and a new bottom hose made a world of difference for me, but maybe your rad. is still very good; a collapsing bottom hose can cause a lot of problems and it's only 20$..) or even a dual electric fan like a lot of people are suggesting.
Anyway, all this to say that; if you start with an electric fan, you're just putting a band-aid on; the problem is still there.
btw; if you don't already have them, I recommend starting your Vette library with the followings:
-service manual
-assembly manual
-Chilton 68-82 Vette repairs (not many stores have Chilton; they have the other one; Haynes I think it's called. That works too if you can't find Chilton)