The schematic is at
http://www.nostalgiaair.org/PagesByM...8/M0003718.pdf
300-0-300VAC @ 100 mA, 6.3 @ 3.5A, 5V @ 2A. First issue is FIT. I'd rather deal with a different voltage than a different mounting size... You could use a Hammond 272BX or DX, if it's vertical mounting, reuse the old end bells if horizontal. I might have something usable if you get the exact dimensions...