supercharger shaft coupler

After doing alot of searching, I've come up almost empty handed. I'm rebuilding my supercharger and am going to replace the snout seal, bearings, and rear case bearings. I was also going to replace the coupler. My question is this, what years of sc's came with a solid coupler in them? Mine is an 89, but the superchager came with a spring isolated coupler. I thought that they only came in later models? Thanks,
Scott

Your supercharger has been replaced at some point in time. The spring coupler was used mainly to reduce customer complaints that the supercharger was noisy at idle. As far as I know 91 was when the change happened.