I replaced by steering box today. It took less than an hour but I do have a lift so that certainly makes life easier.
I’ll try to make the long story short as possible. At Goodguys last month I won a drawing for a Borgeson Performance series 12.7 to 1 ratio PS box. I decided to put that new gear box in my 1984 Monte Carlo SS since it came from the factory with the F41 suspension, which includes 12.7 to 1 ratio PS box.. The SS now drives like the car was new again even though the old box was ok.
Today I put the old Monte Carlo SS 12.7 to 1 ratio PS box into my Checker. The Marathon drove like every other car back then that had 4 turns to the wheel (16 or 17 to 1 ratio). It drove with finger touch and no feel for the road. The SS steering box is identical to the Marathon box externally. It just has a better 2 1/2 turn of the wheel that gives a better feel of the road now. I also changed the intermediate shaft (also listed for the Monte Carlo) since the rag joint was getting sloppy.
As Christian Hutter stated, it’s a standard Saginaw 800 box that is on many, many cars. I do need to add though that I have forward steer, so the application may not work for all Checkers. In 1980 GM went to a smaller input shaft & o-rings on the steering hoses, and also a 1977 intermediate shaft is different from 1978 and newer. Still will bolt right up, you just need to change rag joint and put adapters on the hoses.