I think the differential is the magic part needed to run 2.45's, so if you've got one of those you're good to go. I don't think those 2.45SG's sold for very much, as it's not a popular gear ratio and the diffs weren't good for anything else.

My 74 Swinger with 2.45's got 10-12mpg in town, but 20+ on the highway. The 2.45 1st gear in the 904 just didn't multiply torque enough for the pig to get out of her own way. Out on the open road, she was actually kind of fun to drive. 2nd gear would go a LONG way...

Clair