81 kawa/gpz suspension set up question

[racer 07]

1981 Kawasaki 550 GPZ twin shock. I'm doing a refurbish(not a restore). Needs rear shocks. I do not have the originals. I need some set up info and shock brand recomendation. I don't think it needs a piggyback shock. No racing,some dirt (4miles) to the pavement from my house. A little washboard,sand & gravel. I'm 190lbs 32"inseem. Give me a ball park # for static sag & race sag. (Battleaxe tires) what brand shock, reasonable price. Thanks in advance for any info. Racer 07