[Arran]

No these didn't use the expensive eye tube, just a plain old 6U5/6G5, it was the shutter dial sets that used the expensive and rare eye tube called a 6T5. In terms of whether the 6X5 might be a problem it really depends on the current and the voltage, if the current load is under 70 ma and the output voltage stays under 250 volts there shouldn't be a problem. I've never heard of a 6AC5 power output tube, but apparently it's very similar to a 6K6 in heater current, 400 ma, except it's a triode, plate current is 32 ma, grid 5 ma, the rest of the tubes will be much less then that, hopefully they won't add up to more then 35 ma or so.  The audio amp is very interesting, it has a first audio amp tube that feeds into a 6P5 which acts as a driver tube for the 6AC5 power output, in a cathode follower setup I believe. The resistors in this thing may need to be checked, they are all 1/4 Watt types which I have found like to drift in value in other radios.

http://www.nostalgiaair.org/pagesbymodel...025445.pdf

Regards
Arran