Well that's a tough one... being able to tell the valve in an existing box. There are so many numbers and so many combinations, you are probably best off to go down and get a reman from your favorite auto parts store for the exact fit to your car or truck. After core charge return you are probably way ahead to do that instead. I would be real surprized if you need a 13/16" input because like I say, I believe the 13/16 shafts were used mostly on big cars and trucks, some of which the box mounted outside the frame rails.
To be honest with you, the box I have is a 230 valve, and a 13/16" input shaft. I was ignorant of the differences when I bought this from a race outfit, and I screwed myself for not learning all I have shared with you first. Turns out I learned this box was for a NASCAR Truck and not at all what I needed. I paid about $300 plus shipping for this Sweet reman box, but when I got it I discovered the differences in the shafts, and the 230 valve would not have worked with my 2:1 quicksteer reducer on the shaft of my dirt modified. As I was bragging to a race buddy about my purchase, he was not so kind in telling me how badly I screwed up..
The 230 valve box I have would work for you with power steering, and pretty much most of the GM boxes will interchange bolting up positions. Somebody out there please correct me if I am wrong...?
But, I highly reccomend you go to your auto parts dealer and trade your core in for a box designed for your ride. OR, you could go find one off another vehilce exactly like yours in a wrecking yard...? Then you will have piece of mind that you got exactly what is meant for your ride.
If you really think the one I have may work for you PM me and we can discuss it... Jim