You do not need a centrifugal clutch, but it requires that you pull in the clutch lever whilst yanking on the starter cord, which can be a little tricky, especially if a high compression cylinder head has been installed.
I've never looked back after fitting a centrifugal clutch to my bike; in fact i could not live without one.
The second part of your question will be answered by doing a Google search for:
"Pull-start, Pullstart, Pull Start, 80cc, 70cc, 66cc, 60cc, 48cc,"
the photos and description will make installation of the pull-start self explanatory.