I just put a set of 195/75-14 Michelin X from costco on my 245 (88), for 300.00 tax and everything. I can just say that they improved the ride greatly. Way better than the 100.00 for 4 set that they replaced.

Hawk

This is a handy tool for determining speedometer error from various tire sizes:
http://www.miata.net/garage/tirecalc.html

The original 245 tire was a 185/80-14, a size pretty much unobtainable now.

195/75-14 are almost exactly the same circumference as the originals while the 205/70-14 tires are a little bigger.

I've had both sizes on 240s and they worked fine.

195/75-14 is becoming a rare size these days as well. Probably the best readily available tire in that size is the Kumho Solus KR21. I've never used them personally, and the "Made in Vietnam" labeling I saw on one at a tire shop gave me pause.

There are still lots of choices in the 205/70-14 size. I like the Yoko Avid T4s in that size.

P.S. There are 185/80-14 load range C tires still made in the original 185/80-14 size. The primary market for those is VW Vanagons, but some 245 owners commenting at tirerack.com seem to be happy with them on 245s. Check out the Yoko Y356 http://www.tirerack.com/survey/SurveyComments.jsp?additionalComments=y&commentStatus=P&tireMake=Yokohama&tireModel=Y356&partnum=8R43566&vehicleSearch=false&fromCompare1=yes

On my first 245 (an '88), I used 195/70-14, then 195/75-14, and ended up with 205/70-14 for at least 100K miles. The latter are just a touch wide for the stock 5.5" wide wheels, but I drive pretty aggressively and I never felt it was too much tire or rolled too much for the car. I also kept them pumped up to 36 psi.

Over the 250K miles before the car was retired due to being hit, I ran the stock Michelins, Continentals, Toyos, and Yokohamas. By far the best were the Yokos - the Avid T4 in particular. Good life, good traction and wet handling, and decent steering feedback. The worst were the Michelins (too hard a compound, trading poor traction and handling for good wear) and the Toyos (way too slippery in the wet).

The 195/75-14 has the least speedo error and actually has an improved load range (92) over the stock tire (90). The 205/70-14, as you pointed out, is slightly smaller in diameter which results in a trivial 1% speedo error, and has a load range of 93.

"All weather" tires is a marketing myth, and if you need to travel in snow frequently, bite the bullet and get dedicated snow tires. The M+S rating is based solely on rubber-to-groove area and has no actual performance definition; tires intended for ice + snow have the little mountain peak icons on them and must meet winter performance requirements. Doesn't sound like you need those, though.
--
In God We Trust. Everyone else, keep your hands where I can see them.