What piston kit to go with?

So you guys that have followed my threads know I've pretty much given up on using my mismatched,scuffed up pistons but now I have a dilemma. Should I go with a larger displacement and have my cases opened up or go back with another set of 900 sleeves and 1015 pistons? I don't want to have to do head work other than a valve job and new seals and keepers, so if I go with say a 1045 kit(being able to bore later to 1075 is a plus too), will the 900 head which was ported heavily be able to handle the extra cc's? Cost-wise it seems there isn't much difference between most of the kit's from 1045 till you get to 1100cc and need a big block. I was hoping to go to a 1045 with my stock sleeves but I've seen conflicting posts on it and I live in the deep south so hot weather is unavoidable. Basically I'd like to hear a few more opinions on what I should go with.

Id go ahead and find a decent kz1000 block and sleeves and have the cases cleaned up to fit them,then you can run a 1015-1075 without having to go back into the bottem end again later.
The 900-1000 heads use the same ports from 73-80,no big advantage in either head other than bigger exhuast studs on the kz vs z1

You don't need a big block until 1327cc. You didn't say if the head had stock size valves. If not, it couldn't have too heavily ported.

However, with 1015 or 1045, you should be good.

Valves are 36mm intake/30mm exhaust, thanks for the replies and suggestions.

sc/ant864 wrote: Valves are 36mm intake/30mm exhaust, thanks for the replies and suggestions.

Those are stock size. Adequate for a 1015 but not ideal. They were correct for the 900 motor. Kawasaki should have gone to 38's when they made the motor 1015. The 30mm exhausts still would have worked just fine.

Measure the throats. Not the runners. The throat is the opening where the port meets the seat. That should be at least 32mm. If it's not, open it up.

If you have any doubts on the sleeves, go 1015. Bolt together what you have and go enjoy the bike

Thanks Larry, Jay and Wireman. Once I get a valve compressor I'll post the runner numbers.