15" wheels are an absolute monster to find high speed tyres for. The sizes you are looking for, from my experience, don't exist with a high speed rating. I ended up with BF Goodrich tyres on my MX which only go up to 110 mph beacuse of the width I wanted.
The closest you will find are Toyo R888R's which come in a 225 and 235 width but are only a 50 profile.
https://www.demon-tweeks.co.uk/motor...oyo-r888r-tyre
The only others I can find are from Northants Tyres who supply "muscle car" rubber - this one will go up to 149mph -
http://www.northhantstyres.com/main-...GalVR-RWL.html