i will try to precis this,,,d10 onwards one cam profile on a taper can be set at any crank position some say 18 deg some say 30 deg BTDC,,,,, havnt played with one of these yet to get answers,,,excluding the early d1 lucas,,,,d1 to d7 the cam is held in position with a tiny woodruff key, early wipac magneto had a 12 o clock keyway in relation to the crank pin, the cam looked lumpy,,,later ones up to d7 had 2 types of cam and 2 diameters of magneto bowl wit a slight difference in advance of the magnet positioning,,,,all of these had a 11 oclock keyway position both d7 cams would work but try setting the points to .005 thou to see if it runs,,th long duration cam d7 was for the trickle charge small rectifier, nif you have two much clearence on your spider to magnets the spark could be weaker and have less output for your lights, with magnetos,, no plug suppressor cap!!