If you're interested in quality, skip the zooms. Zoom lenses from the '70s and '80s were notoriosly bad, and unlike a fine wine, time hasn't made them better.
The SMC Takumar fixed focal length lenses have some of the best reputations in the world of 35mm photography. Search the web; there are plenty of sites with reviews of all of the Pentax lenses. A good lens in the 100mm or 135mm range would cost less and seriously outperform any zoom lens frm that era.
Unfortunately, the price of Pentax K-mount lenses has gone up lately since Pentax released the *ist-D digicams. Once people found out they could use these great old lenses on their digicams, the lenses started selling very quickly. Check KEH.com for a good idea of what the lenses are selling for these days.
(You might look for an old Pentax screwmount lens and a screwmount-to-K mount adaptor. These work well, and the price of the screwmount lenses hasn't soared like the price of the K mount lenses.)