I'm looking at a 1974 Cal 2-29 (Jenson). How does this model compare to other fiberglass sail boats of that period. I'm mainly concerned with the fiberglass and blistering as well as any other concerns I should look for.
About par for the course, perhaps a little better than most. The Cal's are good boats for what they are. Unless you have a major blister issue I wouldn't stress it.
Fiberglass is a funny thing, it doesn't age based on the calander, but based on the number of times (and severity) it is stressed. So a boat that was raced heavily for a long time will be much more of a problem than an older boat that was never taken out and used.
While all FG boats blister to some extent, Cals are not known to be particularly prone to blisters. As alluded to above, the overall workmanship of Cal is usually considered to be above average, particularly for that era. That being said, the history of an older boat will have as much, or more, of an effect on its present condition as will anything else. If it has been well maintained, not raced particularly hard, and hasn't had any major accidents, a Cal 2-29 can be a very good choice. The only major problem common to many Cals of that era is that they often had a steel reinforcing beam at the base of the compression post that can corrode over time (a Google search will undoubtedly provide details on this).
Make an offer contingent upon the outcome of a survey. A good surveyor should be able to find any major faults.