On the HEI, I would replace the vac advance with an adjustable unit, also replace the weights and springs. Hotter coil and module will help, too. Then you have to have the balancer set up for advance timing, easiest way is with a timing tape that wraps around.
One problem you have with power is that you have loweer the bottom end torque with the larger carb and headers. To seal the leak, use ultra-copper RTV on both sides of the gasket, and let it cure at least 24 hours before starting.
On the timing gear noise, I would call the engine builder and ask why it's so danged noisy. It shouldn't be.
