After many hours of online searching, comparing shapes of a million different rad hoses for a variety of bikes, I got a set of silicone hoses for a klx220 -- they appeared in the pictures to have the proper bends, so that I didn't have to use so many 90 degree adaptors -- the water flow would be smoother throughout the system. I also got another ex500 rad cap filler unit, and was able to attach it solidly to the frame with an aluminum bracket I fabricated. All the hoses clear the engine with room to spare, and the slicone construction is more durable and will hold up to more pressue.
There is still one 90 deg bend (centre of this photo) which attaches the silicone hose to the mito hose I need to use to make the mito rad work properly.
Notice too I am clamp-free -- silicone hoses require special clamps that have an inner sleeve -- prevents the notches in a typical rad hose clamp from tearing into the outer surface.
Some pukka race kit -- that is an actual HRC overflow bottle, zip-tied to an aluminum bracket I made. Sender for water temp guage can be seen in the background. Not much more to be done at this point. The new carb parts have come in, so I went with a much larger pilot jet to address the backfiring. Hopefully that takes care of it. I also bought a used air/fuel ratio meter. Came very cheap -- hopefully it still works. If it does its job, I will likely get a stainless bung welded to to the header in order to take some readings to set the machine up with some more accuracy.