I am pretty sure that the B30 block will NOT take that big an overbore.
If you could find some 6-bolt 2.13 pistons (6 of them) that is about as big
as I would feel safe with. And what are you going to do for a headgasket?
They are hard enough to find (and co$tly) for a 4 cylinder engine.

Why are the HIF6 carbs not tunable? Are you maybe thinking about the &%%#
Zenith-Stromberg 175CD carbs?

The K cam may help some with performance. Like Paul says, the FI exhausts
and a better intake manifold will help a lot, although most of folks that
I have communicated with about the use of a carb on the FI intake manifold
have not had real good results with it. Dominik Benz of the German 164 Klub
has a manifold (possibly Penta AQ165) that uses 3 sidedraft carbs on an
otherwise stock engine that seems to work very well, especially from the
petroleum producers' viewpoint.

OTOH, I have an old IPD street perf cam with stock B30A manifold on mine,
using an F head with a bit of porting in the lumpy, rough places, and it
is pretty much of a neck snapper at some speeds. (Uses lots of gas, too.)
I am using a pair of HIF6 carbs and they work very well.
--
George Downs Bartlesville, Heart of the USA!