TypeI upright cooled TypeIV help.

[Oliver Knuf]

Use the 1.8l heads, a bit p&p and seat machining will help to get the most out of the otherwise stock engine. Another tip is, that you machine the piston tops 2mm down, so the piston chamber get smaller. Same has to be done to the cylinder sealing surface, but check your top-clearance before.
You can't use the 40's as butterflys for the K-Jet, as the K uses it's own system, the big air washer under the air filter is highly important as is the dual throttle/butterfly to get the correct torque/rpm's your engine needs. Okok, there are ways for all, but I wouldn't do that for sure. Use the injection manifold of 1,8l busses and redesign the jet mounts for the k-jet jets. Build the butterfly part from the rabbit to a homebuilt flange, that you weld on the center part of your injection manifold and go from there to the original air filter box.

Just my 2 cents!