1 3/4 or 1 7/8 headers will bring back some low end/mid range and part throttle response.850 vacuum secondary isn't too big but a 750 with the smaller throttle bore would help the responsiveness also.
I would keep the rpm intake,any other dual plane is a step down.
That cam should be fine but you can advance it 2-4 degrees for more bottom end.
The more work on the heads(air flow)will help everything.No reason that thing shouldn't fry the tires.
Make sure the timing is right as well.