Road Cycling - frame size?

i'm in the market to find an inexpensive, but decent used bike to get me around school and town (college station, tx). i think i might have found one. it's an old school schwinn varsity. the frame size is 55cm. i am 6' 3". i currently have a giant ocr 2, size large. the specs for the large giant are actual frame size: 55.5cm, but it's supposed to be comparable to a 58-62cm bike. do you think the schwinn will be too small for me? i don't plan on riding it for any extended period of time. like i said, mainly just to school and from one class to another. i will have my car there, so even 'around town' is a bit of a stretch, but i can see an occasional ride or two someplace other that school. i don't plan on riding very many miles a day. maybe 2-3 on average? 5 at the absolute most if i actually use it to ride around town. i will have to have the bike shipped, so i won't be able to test ride it or anything.
thanks in advance
-chad

I'm 6'4" amd ride a 26" or 66cm frame
Schwinn

6'3" 60cm frame Fits great
Cannondale

I just had a look at the Giant website yesterday. See, this is why 'Compact geometry' *pulls a face like he just sucked a lemon* sucks. I'm 6ft 3ins myself. The largest size has a 610 top tube, the next size down has a 585. That's a full inch of diference. There's a lot of people inbetween these two sizes, as I suspect there are between the other sizes. So what, you just put a shorter stem on? What a joke.

Anyway, i digress. If you're only riding that far, build up a fixie or singlespeed. Making the broad assumption you're the same size as me, what you need to look at is top tube length. On the road, something near 60cm is what you'd be after, for an MTB, a top tube between 24.2-25" will fit you well.