Finally!

273 said
I've never built a /6 but from what I've read the main problem to decent HP is the head flow some of the numbers I've seen fully ported head flows about as much as a stock 318 head 175 cfm and with 2 less cylinders pumping I think 225-250hp is more gonna be the range unless you go crazy CR and cam.

Yeah... I'm with you. In terms of building one - this will be my first - even my first time taking one apart. I've never tried to look at or use one before...lol. I am a firm believer that the loss of two holes means little in terms of modern building techniques and achieving positive results. Six cylinders just means some changes in the header design and camshaft specs because the firing is only every 120° rather than every 90.
I've been reading up a bit on them, with emphasis on Mr. Dutra's work. I'm learning a l bit specific to the slants, but nothing that is not already a big part of modern engine building in regard to V8s.
I agree that the head flow is probably the biggest drawback - with modern piston choice a close second. I have some skills with a burr and I know I can improve a bit over "as cast" and there are a lot of small tricks to eek out better breathing. With the other ideas I can apply I am confident I can reach beyond 250 if I can get 170cfm on the intake side. I haven't looked yet to see how "bad" as cast is. I know it's small - but that's only part of the headflow equation and not always fatal.
As far as cam and compression go - I know how to build what some consider high compression and my engines don't have detonation issues. I'll have to see what the chamber and block look/measure like - I may end up with a custom piston. That would already allow a big improvement over the old designs in the catalogs. There are much better cam lobe designs than any catalog stuff I've seen for these engines but the limitation will probably be the availability of a decent cam core. I'd hate to have to buy a brand new cam and have it reground - but that may be what it takes.
As I said it's all going to be a process of discovery for a while...lol.