Difference between 741 and 742?

wstreetrod said
I've been trying to get a new set of 3:91's but can't find them.

If you're saying 3.91's for a 741 case then yes new 741 gear sets are getting rare, I'm not sure anyone makes them anymore just 742 and 489. Have you talked to Dr. Diff?

http://www.doctordiff.com/