That 327 has more than enough power and plenty of parts available, no reason to switch to a 350.

My first thought is that you should address the known problems before you jump in on a full rebuild, if you are serious about keeping costs down.

That six pack is Bella cool, but they are known to be problematic.

How do you define performance? For me, the first tenet is reliability. The HP of a motor that won't start is zero. A simple HEI distributor that is rock- solid dependable, out performs a complicated crank triggered MSD set up that doesn't work reliably.