Rear Spring Installation

[Joe/Ct]

I recently did some work on my drive train and did so by removing the rear end, spring and all. I removed the spring to make some repairs, and have mated the spring to the rear end. I am now in the process of re-installing, but am having some difficulty. The spring fits into the channel and I am ably to tighten the nuts to the original u-bolts, but I am unable to do so enough to insert the cotter pins. I have checked to ensure that the spring bolt is in the frame hole, but still no joy. Any suggestions? As a side note, others have recommended that I should have left the spring in and just removed the rear end at the shackles, but I am beyond that. One option is to remove the spring from the rear end, install just the spring, and then install the rear end with the spring already installed.