The 8 1/4 thread

Ok just read the thread in its entirety. Lots of good information. So it looks like memike has the offset rear end and he was able to go with a shorter gear (3.55 I believe) by adding a spacer? And he could not go with sure grip/trac lock as well?

So if mine is indeed the offset, then I can swap gears with a spacer but CANNOT do a sure grip. Am I understanding correctly?