This is difficult for me to answer as we are getting into proprietary information as rebuilders we guard our information which is why I was reserved about posting all this already. In the rebuild process shafts are polished (much like a crank shaft is on a machine) we clean up the gears if there is excessive wear we don't play with it we scrap it (this is called fall out in the industry) we use a simple rule If I wouldn't put it on my car I wouldn't sell it to you. (AND I AM VERY FOND OF MY BMW's) as for Quality I would certainly put any of my units against any other builder especially when it comes to bimmers it is very rare we have a failure in a BMW unit this is why I am not afraid to offer lifetime warranty on the units. (we have had on many occasions the installer that likes to cross thread the threads arrrrrrr now that is aggravating)
I'm happy to sell you a unit but out of curiosity if you already have a 712 tagged unit why would you swap ? if you want to upgrade a Z3 rack would be your go to unit. Changing one 712 for another would be like changing a bulb that didn't need to be changed Just curios ?
As for this thread I can say I welcome any information you all can come up with there is never enough information to compile and I am never opposed to calling an audible and changing my listings on my site to better serve my valued customers. Combining numbers is always a blessing to manufacturer as it simplifies things for those placing orders. So In advance I thank you all for your "positive" contributions to our knowledge banks as I mentioned I try to learn something new every day.
I also thought I would toss this out there for fun. On Many occasions I have found OEM cores returned where BMW has placed a pretty sticker over the original tag with later model digits on them (ya just gotta love that) I have seen this most commonly on the 5 series where the only difference was Internal seals and the way the lines were routed this is a prime place where I combined part numbers to simplify things.
Ok gotta run I have Audi's to build tonight
Oh yeah I also do Audi, Volvo, Mercedes, Honda, Nissan, Toyota, and on and on and on LOL