Ken,
Never used such a cam. Dunno about machining costs there, but for sure are high. But also is much easier to change a head than a cam in a L6, so I'd opt for the head. Have in mind that I do most of my job and machining here is nickel and dime stuff. The cam/lifter stuff ain't for free either. It's up to Ya.
If it were mine, would go for a 8/1 cr on the big chamber head, 76cc or even a li'l more, let's say, 80cc. You must see that this is not possible with a flat top zero deck, it must be at around .160" down the hole with a flat top. So if You can get let's say a 60cc chamber with the very same piston, You'd be with a 9,5/1 cr. Get a cam with a bigger lda than You'd pick for a 250, use the charger. No big pressure too, unless a specif charger cam is to be used. Tired of it, get the small head and go. I use to improve this heads using the 350 heads valves, the 1.94 intake seems right to me, more and it's too close to the cilinder, 1.60 ex. is ok. I'd say that using a supercharger in an engine with such a long stroke and a usable(1,63) rod/stroke ratio is wise. Better than trying to spin it high to get good power numbers. Would opt for the charger rather than the screamer on this one. And to avoid the stress on the crank snout I'd consider a hair drier instead. Seen some turbocharged L6 and they are nice.
As always, just my 0,02.
