1972 Demon 340 engine mods

Update with the Demon!

So all fuel system is now new, tank, lines, pump, carb (850cfm duble pumper that I had sitting).
Cam is swapped with the howards mentioned earlier, we used EDM lifters, billet timing set, its all nice and fresh. This engine wants to rev like crazy, its incredible how it wakes up over 3000rpm.

When swapping the cam it turned out that timing set was shut, chain was so stretched that you could move the cam left to right by a lot.

There is one last thing I need to sort out. Timing curve in the distributor.
Can anyone recommend source for springs and how fast should it advance?
Its all in at 3500 rpm, which I think kills power in lower rpm under 3000.
At what rpm it would be best to have full advance?

Another thing, I set timing at 16 initial and it seems that it gives around 38 total? Is it possible? Anyway, the car idles really nice at 800 rpm, sounds very different from what it used to be. What total timing is best for 340?

I will be putting o2 sensor on the car to see afr values, but spark plugs look really good. The carb that we used I had tuned with o2 sensor on my car before I put it away. It was 15 cruise, 12.5 wot, 14.5 idle in gear (I have 727).

Thanks for all previous suggestions, this car is a new thing now.