Rear-end questions

I just bought an 8 3/4 ( 741 case) the other day and got it tore apart today and it is without suregrip and has 2.76 gears. I was wondering if ring and pinion gears out of a 742 case would fit in a 741 case? Also, i am in need of a suregrip assembly, what is the going rate for these? And if anyone has one for sale? Also can they interchange between different rear-ends? Like maybe a suregrip out of a 8 1/4 fit into mine? From the way things are giong, it looks like i will have about $1,000 into this. Which isnt what i was hoping for.
Thanks,
Joe