classic motorcycle forum

Hello, was just wondering if someone could help me. I am looking for a copy of the very famous book " Boost Your Bantam" by George Todd. I am currently rebuilding a 1951 D1 Bantam 125 I purchased mostly complete but in several boxes. Heaps of fun. When I purchased the bike not only did it come with the standard oval(teardrop) head but I was also given a square shaped head that looks to have twin sparkplug holes in it. I was told this was a racing head. Could someone please clarify that. Thankyou for any help,information or suggestions one might be able to pass on. Cheers Darren (NZ).