Penny Red Perf Plate Numbers?

I am trying to learn how to plate some stamps I have aquired and have started with this penny red. I have the SG SS Cat but am at a loss where to start?

I have managed to work out that the stamp is from 1855 thru 1864 and must be from plates 1 - 70 as there is no number in the magins?

Any help you be appriciated as my experiece is limited and I have about 15 of these but i'l keep plugging away?

i think it's Die II and either plate 42 or 33?

I am learning along with you, waiting for some answers.

http://www.kernunnos.com/Philately/GBQVLE.html

Found lots of good information on the net, including the link above; but there is a lot to absorb. Barb