I keep reading that it's 1.812" but my measurements are 1.832" Am I measuring this wrong?

I'm not sure about that number.

I do know that the 400 I built for my van, which was a 76 I think, they were .100 to .130 in the hole(yes that much varience)

Hope this is of some help.

put the piston upside down on your table w the flat side down with it slightly off the edge so you can measure it & slide the pin out about an inch & with your 2"-3" mike measure from the bottom of the pin(the top now) to the deck & subtract 1/2 of the pin dia and be aware some KB pistons have a slight quench pad ~.035" or so that is not included in the CH dimention and you would measure to the flat adjacent to that pad.

I've measured a couple o mine recently, and i get .100 to .110 in the hole across the board. Guess i'm lucky, they can really be all over the chart. I'd say those are easily possible numbers.

Just once i'd like to break open a 400 and find some nice KB or forged zero-deck pistons...

Well, guess my measurements were right.