Don't use any timing retard for starting unless you need it. It often causes what it is intended to fix ( kick back ). But if you needed it, 10 would be plenty. As for welding? the MSD usually requires removing the gear roll pin and one or two small fasteners below the weight pad and pulling the shaft out of the independent rotor mount piece then replacing it either in the small round hole to lock out timing change or the elongated one for mechanical advance set up.
Bruce