im looking to regear my 99 3l from a 3.73 to a 4.88 for 33's. im looking for advice as to where people have bought theirs from and what works well

 

I purchased my Yukon brand gears from here: Randy's Ring & Pinion

 

R U planning on going to 35” tires soon…
To me, the 4.88s will be a little deep for highway driving, you will definitely get a seat of the pant feel form the lower gears.

If you do the math you will see going from 31s (stock) to 33s you should run something in the neighborhood of 4.30 do 4.56 will be the best match for added power and a better than stock response.

Just commenting not trying to get you to change.
What do you plan on doing with the truck, off road a lot, just trail riding or mostly highway/street ?

 

^ I agree. I have 4.88's now with 33's and if you are planning on driving it on the hwy or over 60 a lot then you may want to consider 4.56. The 4.88's are great if you going to be doing a lot of trail riding or driving around town though.

 

One more thing... you have 4-low for extra power off road.