suddenly overheating... how bad?

[sd88supra]

when my 87 idles a lot, such as in very heavy traffic (or crossing the us/mex border), my baby suddenly starts to overheat, as the temp gauge indicates. my question is, it neither smokes nor feels significantly hotter than if it were running normal. however, im not gonna take my chances and ive been avoiding the possibilty of hitting heavy traffic. my guess is its a bad fan clutch. im not losing coolant. as soon as i start driving normal again, the temp gauge quickly goes back down.

so, bad fan clutch? i also dont have a fan shroud but neither does my 86.5 and that one doesnt have heating problems (and seems to have a much stronger fan clutch). i think ill switch over to electric fans...