Yeah, 65 is scary enough on the pike...I sure wouldn't go 50 or anything like that.
What size tires? I imagine a common inexpensive size, should be able to score plenty of all-seasons on Craigslist or at junkyards for $25 each, maybe even on wheels that fit your car, with plenty of tread. Save the snow tires for winter.
BTW if you want to come to my garage in reading, I have a set of tire machines to mount & balance whatever you want. So you can order something from tirerack.com or even get some used tires, I'll throw them on for you.