What year is this 250?
It sounds like an intergral head with the intake and exhaust cast as part of the head. They did make some of these with dual exhaust outlets. I haven't messed with one, but if the manifold plenum is common to all 6 cylinders with just 2 outlets instead of one, it won't sound the same as a split manifold where the front 3 cylinders are totally separate from the rear 3.
Generally, it's recommended to stay away from the integral heads due to potential cracks and the lack of ability to upgrade induction.
JC Whitney used to sell tube headers for these, maybe they still do. Would probably be cheaper than Clifford. Otherwise, Tom Langdon sells a real nice set of cast iron duals.
As for the diverter, I'm not sure I would get too worried about it in SoCal. Block it off, and it should be fine. At least until you find what you really want. Studs can be replaced.
