shop told me with 8 inch lift 37 13.50 20s id only need to regear to 4.56s from my stock 3.73s after they did the math.. is that about right or should i get 4.88s?

 

I think 4.88 is better for u. I have a 6 inch lift with 35/12.50 tires and i have 4.56

 

4.88s. I have 4.56s with 37's and while it's fine for daily driving, it's a little weak on low end with steep grades and towing. I still have plenty of top end left so in hindsight I would have gone 4.88.

Another thing the charts don't account for... while the 4.56s put you close to the stock ratio, it doesn't account for the significant extra rotating weight and resistance of 37 x 13.5 tires. The little extra you get from 4.88s help make up for that as well.