[1968CHEVYC10]

I used a walker to rebuild my q-jet. Worked pretty well, stopped the backfiring when I down shifted. don't know about mileage cause I never checked it. I'd also recommend getting this book, "How to Rebuild and Modify Rochester Quadrajet Carburetors" by Cliff Ruggles.
A huge help if you've never done a rebuild before and with alot more detail/info than the instructions that come in the rebuild box.