5.9 magnum with M122 blower/intercooler

Probably not just due to the added cost. With my new engine I've calculated 450 HP without the addition of water methanol. This is nothing by today's standards but not bad for "old technology" & 323 C.I. The design of the Magnuson is more efficient than a traditional roots supercharger in that it generates far less heat and only requires 1/3 of 1 horsepower to operate (compared to 25 H.P. or more for a roots style). Due to this and the 3 lobe design, it is very common to see small displacement superchargers on larger engines that appear to be mis-matched or undersized.

I can't speak to your 408 and 162 combo without knowing head, valve, manifold and carburetor details at a minimum but that should be a really fun combo when sorted out.