Thinking about a turbo slant...
It can be done inexpensively with good results according to this article. I have a slant, and I'd try it...but I think the hole in the side of the block might leak all the boost out! (that was a joke, har har...)
http://www.allpar.com/fix/holler/slant-six-turbo.html
I thought about a small draw thru turbo for my 440 like the old Rajay ones for Winnebagos.