S1 200,

As your say post says cosworth timing i assume it is on a yb cosworth
engine, With the dizzy it is easy enough, just check the cams align &
the engine is @ TDC on no1 cyl comp stroke, then if you then remove the distributor it is a bit trial and error, hold the dizzy so the spring clip of the cap,points to the engine block and the rotor points away from engine
then as you install the dizzy the rotor arm will turn ,if you look on the
body of the distributor you will see a scribed mark when installed the rotor
arm should align with the mark, indicating cylinder no1 in relation to the cap. SO YOU HAVE to judge it, needs to be correct for the phase timing.

DAVE R.