I just picked up some of those mac motors
having a look in side its good to see proper tansfer ports
was worried about the lack of thrust support but figured it out and its easy
there is room on the crank to put a needle style thrust washer as well as shims.
they will only run on the bottom half of the case but this is fine
You will be able to shim the engine so its right
its a cheap and great solution and will last forever.

the good thing about this engine for is how thin it is
of course it gets wider with the exhaust on the back
but the front mounted carb looks great and with a velocity stack on it will look awesome

ok am trying to load some pics to explain what i mean but i cant