340 valiant build advice needed.

I guarantee you that you will not like a street engine with power at 7000 rpm.
With 3.23 gears,
1) you can be speeding at the top FIRST gear. and
2) top gear is calculated to be ~180 mph, a speed your 340 Duster can never achieve., and
3) if yur not careful, it will be a dog off the line

For an Iron-headed 7000rpm engine, you will likely need 4.30 gears or thereabouts, and then, cruising 65= 3500 or more, so now, you need an overdrive. and altho 4.30gears will make her less of a dog off the line, having run this combo myself, I can't tell you how stupid this was.
And not only that, how far can you drive on the 66 liters of gas in the tank?

IMO
you need to rethink that.
I did and ended up with a real sweetheart.
Just put the Power-peak down around 5200, install some nice Hi-flowing alloy heads on her, pump the pressure up close to 200psi, and install some valve springs that can hit 7000, on occasion without pumping up. You'll be many many smiles happier.