I assume you mean the original late 60's early 70's Ranger 26? Not the Mull design of the 1980's.
These were pretty well built boats but 40 years is a long time. I haven't heard of Rangers having worse corrosion than other iron keel boats of the era. Unless the owner can show you paperwork of replacing the
keel bolts, just assume they need to be replaced. The new bolts will be good for longer than you'll own the
boat. Same with the stanchion bedding. Unless the owner's already done it, assume they have to be unbolted and the bedding replaced.
The wildcard is
rot in the balsa cored
deck. Don't be scared off by a few small soft spots - very few boats of this age don't have some. But big rotted areas are simply uneconomical to fix on a low
price boat like this.