Rear Shocks for '81 KZ550 ltd

Took the bike out today for about a 15 mile run since getting it running well enough. 28 year old rear shocks plus my 190lb fat ass make for a rather "squishy" ride. Yeah, I know, the KZ550 Ltd is NOT a sport bike, but I'd like something a little firmer. I've adjusted them to the most stiff position but I think their age has done them in. Anyone know of a good cheap pair of rear shocks that would provide a more appropriate ride for a 190 pounder? Looks like they measure about 13.25 inches when fully extended when the bike is on the center stand. There's a pair from Z1 enterprises for under $100 but don't know if anyone's tried them?

Some suspension websites:
1. www.progressivesuspension.com
2. www.racetech.com (front suspension rebuilding service)
3. www.hygearsuspension.com
4.www gpsuspension.com

And www.denniskirk.com and www.jpcycles.com

You can cruise ebay for a set of Sportster shocks. They are close to the right length (measuring eye-to-eye) but the drawback here is the eye diameter is wrong and you will have to find new bushings or use the old ones from your original shocks. You may also find you have to spread the lower shock mount on the swingarm. I've picked up brand new take offs for $30.00. The sportster is a heavier bike than the 550 and I have found, being just a biscuit over "substantial" myself that these shocks are a far cry better than the 28 year old OEM's. Good luck, ride safe.