rotate the engine to top dead centre firing (You can check your cam position to do this or just assume you are on firing stroke). Place the dizzy in with the rotar pointing towards number one plug on the dizzy cap(you may need to mark the housing of the dizzy at the number one plug position). Try and start. Does it start or does it back fire? If it is back firing your dizzy is 180 degress out. Just swap the lead on the dizzy cap 180 degress ie if you firing strok is 1342 and the leads are configured like this
1 3
2 4 on the dizzy cap
the swap the leads to this
4 2
3 1
Not the firing order is the same but lead configuration is rotated 180 degress