Help bolt pattern on diff is diffrent!!!

[svxsubaru1]

I am doing a 5spd swap in my SVX today i was hoping to finish so i was working on it. I was putting on my drive shaft and it went into the trannie with no problems, but then i tried to put the 2 inch extension on the drive shaft ( 5spd is about 2 inches shorter ) and bolt it up to the rear diff, i was trying to put the bolts through when i noticed that the drive shaft extension had a larger diameter than the diff bolt patern part, then i tried to put the bolt through it and sure enough the bolts would not fit, i could only get one in. So i spent about 1/2 and hour looking and tring to see if i could get it to fit, i figured the bolt holes werent evenly spaced out, unseccesull i went inside and measured my old diff from the auto, the circle were you bolt it to the drive shaft was about 3.25 inches, I then went out side and meared my new diff, it was only at most 3 inches. I got all of my stuff from a 90 legacy wagon with a 4.11 diff ratio, the stock rear end on a SVX is 3.545, both are r 160 diffs or should be. Whats wrong???