Search the internet for all the information you can about those cars. Your goal is to know more about them than the seller. Find a local car club member who knows even more about them to take with you to look at the car. Don't buy it sight-unseen unless you (literally) have money to burn.
It's current condition is the most important thing. Until you see the car in person and look for rust and anything else that can/will be wrong with it you won't really know. Photos from the seller will not do.
After you & your borrowed assistant have seen the car and discussed what it will take to put into an acceptable condition, it's your decision on how desirable you think the car is, what it's worth to you, and is the seller asking too much....