How to mix 4:3 and 16:9

I have footage in both 4:3 and 16:9. I captured both on thier own format. Now I want to edit them and have the final movie in a 16:9 ratio.

Both were recorded with standard definition cameras, how do i mix both fotage without affecting the picture quality and if possible avoid too much rendering time.

What are the setting I need for the sequence?

Thanks for all your help!