I have a 68 Impala with the 327/275hp V8 in it.The car has factory A/C.The fan clutch started sqeaking the other day,so I think it is starting to fail.Do I need the 7 inch or the 8 inch clutch on the327,never had an old chevy with this on it.Any help would be greatly appreciated as I understand there are a few different ones for different applications,thermostatic non-thermostatic,etc.

Try NAPA

I would try Napa or advance auto parts,but when there are several different ones avaiable and they are not sure which one fits,I would like to get a better understanding of which one I need before I get to an auto parts store.Does that make sense?

The original was termostatic....note the coiled thermostatic spring facing the front. This would be the best and most expensive one to get.

So if you give the parts place the year model, size engine & HP, whether it has factory A/C power steering, power brakes and automatic transmission and they don't know which fan clutch to buy, check Rockauto and look up your options. That may be the best place to find parts for your car, I have bought engine parts, filters, and a lot of stuff there.
Check them out here: Rockauto fanclutches for 68 Impala 327 engine
I used the Hayden Thermal fan clutch, it comes with a bushing, which you may or may not need.

Just looking at a parts listing I have and it says Fan Clutch Assy.1960-67 Chevrolet 3814137. Maybe 1968 is the same. Just thought maybe you could cross reference the number??
Neil G.

Mr Mack, thanks for the info.I have the same exact driveline that you do,this was the information I was looking for.Thanks again!