I don't think you'll find any specific data for the Winchester bullet and Rl 15, but if you use the data you have, and follow the old axium of starting low and working up all will be well.
34-36 grs of rl15 is usually where things come together with the 150's depending on the rifle, brass, primer etc.
Speer and Alliant are owned by the same parent co. That's why the all speer bullet data on the web site.