Loss of power with new cam

Built slants like around 30 degs of total timming. No more than that.
Use a timing light with advance,to set your total timming. Set your total around 28-30.
At this point,whatever your initial is,it is. My guess,working with slant distributors,your
"initial" will now be around 16deg,with your 30deg total.

At this point,don't worry about the curve of the distributor,or vacuum advance.
Plug all the ports for vacuum advance. Once you get the car running decent,then you
can start playing with those.

Go back and check the obvious. Cap,Rotor,Wires, Firing Order of wires,Valve Adjustment,Ect.
I've seen brand new caps,or wires that were crap. Give everything a thorough
inspection.