Any tips for setting timing dwell on the 273HP

Need to set timing and dwell on the 273HP with clean air package and manual trans.

Not much experience with the dual point distributor I guess the dwell should be double the book setting for a single point is that right?

My book says timing 5 degree after TDC is that right? My book only goes back to 1967 but I'm working on 1966 with the clean air package.

Non clean air package timing at 10 degree before TDC. Big 15 degree difference between the clean air package and non clean air package timing.
Wondering if there is any performance to be gained from advancing the timing a little on my clean air package 273?