Big blocks with pull starts have a tendency to snap strings when they are new. Once they lose a little compression the pull start will last just fine. If your engine is tuned well it will start very easily after it is primed.
I forgot to put my Losi spin start back in my car after a bash one time so i put a pull start on my Mach 427 which worked fine. I got my losi pullstart from Killerhobbies.com