I have restored a number of radios and phonographs, but never a battery powered one. I would appreciate any suggestions regarding a battery set-up for this 1946 Echophone EC-600.
Thank you!

The batteries (90V/1.5V) spec'd for this "farm radio" are Eveready 748, Burgess 17GD60, Ray-O-Vac AB82. Is there anything modern that would fit in the cabinet?

Not really, you can daisy-chain 10- 9 volt batteries for th 90 volt, and get a double d cell holder and parallel those for that voltage.

Yes, I thought of this setup to at least listen to the old bugger. I wonder how long the radio would play on the chain of 9-volters?

Like the average battery set, the quality of your batteries will be the determining factor, along with the volume you play it at. Various dollar stores have them, I would start with those. Walgreens' has some deal on quantity purchases, also.

I think I will grab some tonight after work and try it myself

Those 9 volt batteries could last a good long time if you keep the volume pretty moderate. Could not hurt to measure the current drain on the B+ to get an idea of what the demands are. Using alkalines is great, the old batteries might have been larger but were probably that zinc carbon technology so the original users probably could not have gotten alot more life than you can with modern formulations. I have daisy chained batteries for years to use with one or two tube sets, the battery life is inestimable, as I have not run any down yet, being that my usage is so sporadic. Filiment batteries are another issue, and a rechargeable filiment battery is of value here for most tubes.

Here is some good info!:
http://www.antiqueradio.org/bsupply.htm

I've done that with my Silvertone 2441, with a pair of "D" cells in parallel for the filaments. On cheap dollar store batteries, and played at moderate volume, and played for several hours every day, the "B" supply lasted about a month, while the "A" supply lasted a couple of weeks. And, as I said, that was with a LOT of playing plus cheap batteries. Of course, now I use a Powr Shiftr battery eliminator, but I save the battery pack for power outages.