The cylinder heads also have a good part to play on how much duration you need. If they're stock out of the box Edel's, then you may need to add a little more. If they've been CNC ported or worked over by hand (by someone that knows what they're doing) then you don't have to add quite as much duration.
There's no reason not to make horsepower with this engine. The cam would definitely hold you back and I think anything less than a nice big single plane intake would bottleneck you as well.
Make as much horsepower as you can within the range that you're gonna run. Cobras have gas pedals, you don't have to hold them down all the time....(Although they're more fun that way....
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