I have some experience with occ's
my son-in-law (azvinnie) has built 4 or 5 so far
the sprocket and engine both need an adapter (the engine definitely and the sprocket is a lot easier with the adapter)
to clear the rear brake, the tensioner needs to be mounted upside down, pushing chain below brakes
there are 2 different engine mounts available (livefast motors, and a guy called barry something on e-bay), we had probs with livefast's mount and have used barry's on every build (I even used barry's (with another plate I bent) on a deviate chopper I built last year
I hope that wasn't too long-winded, and will try to answer any other ???'s you have

__________________
Bill (aka azbill, aka azkronic)

yesterday is history,
tomorrow is a mystery,
but today is a gift...
that's why it's called "the PRESENT"