Basically it does just fit together lick a lego set. The runners fit into the head flange, and the velocity stacks fit onto the runners. Then the plenum base fits on top of the velocity stacks. After that a plenum is formed from 0.125" aluminum sheet metal. I'm personally not machining these flanges, but am CAD capable and can design whatever needs to be designed. I just need a cylinder head in front of me to work off of and get precise measurements with calipers.
The runners and velocity stacks I'm using are from http://www.rossmachineracing.com
I'd love to come check out Rusch Motorsports. I'm going to be gone at Sasquatch music festival this next weekend, but sometime in June would be very cool.
Regards,
Justin