You can buy a stock Lares steering box with the correct ratio off of Rock Auto. It will be a remanufactured unit. You can also get the stock box with a faster ratio as well. I went from 4.5ish turns lock-to-lock to a 3 turn due to a tight turn getting into my garage. It was a good upgrade.
Beware anything aftermarket - if it changes the Pitman arm location, angle, etc. and thus the steering geometry, all that hard work you just did overhauling the suspension will be for naught as you won't be able to get it aligned.
1968 Impala SS