If the amplifer has an 8875 .. it is probably a Dentron MLA-2500. 8875 is no longer made and rare to find as NOS -- it used conduction cooling. Some users have converted these to other tubes - BUT require addition of forced air cooling (e.g. blower/fan).
If you want to buy and amplifier, spend an hour and read the eHam revioews and perform a GOOGLE search on the 2 or 3 candiates that you are interested in.http://www.nd2x.net/index.html
Avoid the "sweep tubes" amplifiers -- they were built in the 1960s and 70s when sweep tubes were used in TVs - plentiful and cheap. This is no longer the case -- the resale value on these amplifers is dropping fast -- some are being modified to use available Eastern Europe sweep tubes (El509/EL519) -- or surplus Russian miltary tubes (e.g. GI7b)http://www.geocities.com/ko4nrbs/
Lawson Summerrow, W4EMF has performed a number of conversion and has web pages on the documentation.
Dentron Clipperton QROhttp://www.nd2x.net/W4EMF.html