Volvo 850, cosmetically very nice but blown HG for $600... good deal?

[Mölyapina]

So I'm looking at a potential Volvo purchase... here's the ad:

1995 Volvo 850 GLT body/interior near perfect...

The scoop on it is that the car is cosmetically in very nice shape (the interior looks super, the body decent), and it has 90,000 miles on it, but an overheating issue. The owner replied to my e-mail and elaborated on the overheating, saying that it had begun to overheat a bit during local driving but seemed good on the highway. He had stopped driving it much, but thought that maybe it could make it for Thanksgiving. Unfortunately, on Thanksgiving, it started to lose power and blow white smoke, so he stopped driving it and thinks that the HG is blown.

He wants $600. He's offering to cut a generous deal on a timing belt, WP, and tstat that he bought for the car. I can get a Fel-Pro gasket HG kit from NAPA for $150 (sales tax included), and although I'd hope that the head isn't cracked, if it is, I can get a Clearwater rebuilt head for $500. That means that with a good head, I can get a very nice, low-mileage 850 for ~$800 + sales tax, and if the head is blown, for ~$1300 + sales tax.

My thinking would be to drive it for a few weeks, see how it compares to the Buick, and then sell one of the two (honestly, the Buick would probably stay). I figure I should be able to make a little bit of money on it and have fun with an 850 at the same time. Volvo is a brand that is close to my heart, which is why I was searching Volvos on CL in the first place... . CL is not good for me.