How rare is a 300cc kit for an air-cooler 250r?

[N8s250r]

I recently bought an air cooled 250r locally and it turns out it has the factory 300cc bolt on kit from honda. flipping through old magazines i found that honda offered this kit when the atc was purchased. My 1984 atc 250r has the 300cc bolt on kit, how rare is it. it also has a Nasa +4 super and the origal tool kit in the tool box with an origal Honda Ngk b8es spark plug. the three wheeler still has excellent compression and starts up 9 out of 10 times with one kick. it is completely stock except for the 300cc kit. give me your input on my Find. Thanx
-N8s250r

[deathman53]

the cylinder itself isn't that rare, the pistons and rings are, as well as gaskets.

[3Razors]

The 300 kit is the hot set-up for the aircooled 250r. Piston and rings are getting rare for it though. Take good care of it and very important to keep a UNI filter on it and clean and oil it regurlary and it should last a long time. I did here a rumor a while back that Sudco still has some pistons for it.