this 4.27 we speak of... the one from an e34. I presume that it is an LSD unit? much like the 4.10 automatic diff for late model 325i/iS e30's???

if so then finding one might not be that hard down here in PR there are a couple of junkers with e34's... odds of them knowing what diff is inside and how much its worth are pretty slim so you could get a good deal!

Mike