The casting number is 3769717. One resource tells me it's a 1959-1962 261, but I didn't find too much else.

https://c1.staticflickr.com/9/8848/17756724739_47614d287a_z.jpg

I pulled a taillight bulb and it's a 12V 1157, and there's a huge resistor hanging off the heater control knob so I think the conversion is done. It still has a generator though.

https://c2.staticflickr.com/6/5348/17942891955_518982cb99_z.jpg
https://c1.staticflickr.com/9/8876/17322381123_fa63f895c3_z.jpg

If these photos don't show up, go to https://www.flickr.com/photos/19491433 to see everything I've uploaded so far...