kz1000g vs gs1100,gpz1100

im sure if i get it running write after the swap it;ll have plenty enough for me:)

With 3 babies I do not know if testing the top speed is a good idea. The 1000 will get you there in a hurry, might not be as fast on top end but will haul the mail just the same. I have a GS1100 shafty and a Z1 900. I enjoy both but have more fun on the 900. The dependability is excellent for the age. You should be happy with the Kaw.
My 0.02 cents

If the FI is working ok stick with it. My G1 Classic has done 47,000 mile and runs like a dream, starts on the button and is ready to go, don't have to think about choke as on carb bikes.