The car is overheating at highway speeds. Sitting at idle, she stays at 175, doesn't go above at all.

At startup, and while she is warming up to about 100 or 125 degrees, there are a few puffs of white smoke from the exhaust, but afterwards, nothing. There is an issue with the muffler where I can't completely close the clamp on one side, so I am hoping maybe that's just some errant water in the exhaust, maybe some dew or something like that. I have a guy with some better tools than my set and he will tighten it up or remove and replace the nut and bolt on the muffler but that's not till Thursday.

I have read a few posts regarding "burping", and even found one post that said that the 450's need burping more than anything else, otherwise overheating will result. The descriptions are somewhat vague, though, I am finding, and I am not too sure how it's exactly done, but will try to make further inquiries on that.

Also, I have access to a dead 450sel, with no damage to the front, so I was actually thinking on possible radiator replacement, but the 450sel is 150 miles away, so I would rather rule out everything else, really. I would assume there is no difference, really, in the radiators. Was also thinking on going to a drive-thru oil change place that also does radiator flushes, maybe see what happens after that.