Does anyone know off hand whether the typical Eichler rough in is 12 inches or not?
Our 1958 Jones & Emmons (model JE 724 in San Rafael) has a 10" offset in the hallway bath and a standard 12" in the master. We discovered this after buying two Toto Drake toilets, found that we needed one with a 10" offset, and then learning that Toto did not make a Drake with a 10" offset. Our plumber discovered the variance; hopefully you can determine if you have the same issue in fewer plumbing hours. Good luck!
this is very easy to figure out, measure from the wall behind the toilet to the screws that hold the toilet down ( the ones on either side). That measurement to the nearest of 10,12 or 14 (without going under) is your rough in. In other words if the measurement is 13 inches, you have a 12in RI. Just make sure you measure both, they could be different.
I just bought and installed two toto dual flush toilets (both 12" RI), they are GREAT! (my son thinks it is funny that I get so excited about it).