Rearend modification costs?

I used to swap pigs too. I had at least one of nearly every ratio from 2.76 of course, on up to 4.30s, plus a 4.88s, and a 5.38. But I got tired of that chit and got me a GVOD. Cost me 23 pounds. But I swapped out the cast iron A833 case, for an aluminum one, and broke even. BadaBooom.