No offense but Fred Bear online in the bow identifier lists some of the 50s era bows having 30 and the three years of Alaskan listed as 28 for maximum draw.
Evidently it depends on the model but most were 30 inches unless later one when, as papalapin says, they quote it as "unlimited".
I dont think Id worry too much about anything after 1960. That said, these are old bows and several have had em blow, regardles of draw length.
Like anything, as it ages, any issues will magnify even at 28 inches.