After checking into it, I have a 1985 Monte Carlo SS steering box and my front wheels do not turn fully each way, which is a pain in tight places. The box was bought at NAPA and is too old to return so I may just buy another box. Since I already have my car set up for the newer boxes, what model vehicle box has the correct wheel stops in it that I can just bolt in and drive?

The 85 Monte Carlo SS gear has 78 degrees 30 minutes of total pitman arm travel. You posting doesn't say what year Chevelle that you own. Most of the early Chevelles (65 thru 68) have 87 degrees of travel. That would is quite a bit of difference.

If you own a newer Chevelle the gear travel is something like 81 to 83 degrees (which is closer to your original travel).

The following excel charts - posted at www.corvettefaq.com/A-car.asp (http://www.corvettefaq.com/A-car.asp)
might be of value.

http://www.corvettefaq.com/acar/1964-74ChevelleStrgGearBoxes.xls

http://www.corvettefaq.com/acar/1968-93NovaMonteChevyIIStrgGearBoxes.xls

BTW, your MC gear can be modified for longer travel by taking it apart and removing an internal snap ring and by replacing the aluminum end plug with one that allows more travel.