Kinda hard to square your tech support answer with the B&S website:
http://www.briggsracing.com/display/...p?docid=101243

It shows clear references to the kart world.

Terry wrote:

I just spoke with B&S tech support. They told me that none of their
new engines are recommended for go kart use. B&S wanted to get away
from that market for liability reasons and stuff like that.

But I did ask what the differences were between their older go kart
model. Besides the obvious tilted cylinder, and OHV setup, the main
difference for not using them on go karts is the throttle setup. All
their new engines have a stiff throttle setup that does not return to
idle. The older model 136200 (for go kart use) had a return spring.
One other difference is that the new engines have a float bowl
carburetor design.

The engine can be mounted up to a 15 degree angle front or back and
still get proper lubrication.

They also stated that any B&S engine used in a go kart application
would void the warranty. Just repeating what I was told.

Sounds like this new engine will work out great for my application once
I modify the throttle assembly to work properly with a return spring.