Can I used a 150cc head with a 155cc cylinder?

[santacruz]

I needed an exhaust gasket and ended up buying a 58.5mm big bore kit that doesn't include the cylinder head, along with a 7" 'racing exhaust', an A9 cam, and a main jet set.

Can I use my stock 57.5mm head with this kit? Is an A9 cam ideal for a quick 3 mile run to campus? I'd like to be able to accelerate with cars at leaving the stoplight, and I don't think I'll ever got over 55 mph. What should I rejet to? From what I've seen online, I was thinking 125.

Finally, is there anything I should do to the CVT with these upgrades?