The thing that is hard to find is the original "tech manual" for either the 25 or 77 set.

I have seen ONE hard copy in the last four decades.

However, via the magic of the inter-tubes: http://www.radiomanual.info/schemi/S...67-12_1987.pdf

Getting either unit tuned or repaired without this document is a nightmare.

The original Magnesium batteries are a non-starter as well, but it should be relatively easy to cobble up something that would fit in the battery compartment. For those with the "vintage" 25 sets, you have to also ensure a low-voltage "heater" supply for the "valves" (thermionic tubes).

The vehicle-mounted "linear amplifier" cradle/adapter is a cool bit of kit for the truly hard-core. See: http://www.associated-ind.com/pdf/ANGRC160.pdf

For bonus points, seek out the RC-292 antenna kit. Manual here: http://radionerds.com/images/4/42/TM_11-5820-348-15.pdf