98 blazer 2wd rear end in an 87????

I have an 87 s-15 and I got a new rear end from a 98 2wd blazer. I noticed after measuring the yolk, that it seems to be offset from the center of the frame towards the driver side about 1/2" The rear end is centered in the frame, and I am just wondering, why the yolk if offset. I measured the old rear end and it does not seem to have this offset. Anyone know if the rear ends are the same or are they different, and if so, will the rear end work for my application. Any input would be greatly appreciated.thx