Depends a bit on what you want it for. If you are going to sporterize in a different caliber, the barrel doesn't matter. If you want a collector piece or just a good quality shooter, that is another.
There are no rifles in 7.62x54R in any quantity except Russian and a few Chinese. These can be the old Mosin-Nagant bolt action in either the full length rifle or the carbine. There are also some Tokarev 1938/40 semi-autos around. The "Toke" is long and clumsy and not really suitable for a sporter, though a desireable collector piece. The bolt actions are OK if you don't mind the rather stiff action, but they are not suitable for any other cartridge.
In 8mm Mauser, the world opens up. There are Yugoslav Mausers, mostly ex-German K98k's and Czech Vz24's. There are some Mausers made for Iran in Czechoslovakia, and some made in Iran. There are Turkish Mausers. All these are in 8x57. There are ex-German rifles rebarrelled to .308 Winchester (7.62 NATO) in Israel and other countries. There are Steyr-made Mauser 1898's rebarrelled to .308. There are the excellent Swedish Mausers in 6.5x55.
In other words, the variety is large and bewildering. Of the 8x57 rifles, I like the Vz24, but most are not in very good shape. Most Turkish are not either, though some clean up well. Some Yugoslav rifles are rebuilt and look like new. The Yugos and Turkish rifles mostly run well under $100 even for ones that are fairly nice. Others will be higher, depending on condition and caliber.
Jim