Exhaust: obviously your own decision, but 1-3/4" is smaller than I would use and gives up some power. The usual argument against (low exhaust velocity = reversion) is completely removed by the blower flushing the chamber constantly during overlap.
I could drill&tap them for ?holley? jets that are wide ranging an plentiful.
Exactly - if the "power" orifice is drilled, and you can interrupt it in the casting (some require drilling in 2 places, and routing the passage to outside - not fun), insert a replaceable jet. The tap size is based on wall thickness and OD, there are some very small jets out there, many thread sizes. My (still future) book gives many alternate jetting components by thread, tap and available sizes. In addition, Jenkins used a piece of fine wire draped through a small jet to make really small changes (like a miniature metering rod).
Pan depth: that will help a lot. Keep the same depth over the pick-up to lower the oil down from crank contact.
I'll just move the manifold ahead so it'll line up the blower
You have to be very careful here, because an error is very expensive to fix. Moving the plenum changes cylinder distribution quite a bit, and inserting dams and dividers is dyno work - long and painful. Agreed, that any manifold has some distribution problems (typically #3-4 run rich due to short runners), but a centered plenum is at least symmetrical front vs. rear. Most aftermarket manifolds have fair distribution, but the rotor discharge pattern bias (favoring the front) means don't expect the same with the blower. Moving the manifold introduces another variable.
Just a thought: you're going to make a transition piece to mount the carbs to the 6-71 intake, yes? Making multiple bolt patterns will allow you to move just the carbs back and forth without moving the manifold - not as good, but still worth adding, costs nothing. Just figure out your throttle plate width (1st to last, remember they can be 4 × 1 or 2 × 2) vs. blower case opening length to see how much wiggle you have.
