http:// gnosis.org/library/marcion/antithes.htm
The clues are all there, people just never looked the right way. The God of the Old testament is not necessarily God the Father which Jesus refers to.
Try reading the Old testament and REALLY pay attention to the different ways "god" is referred to, and remember that lots of times, things have been intentionally distorted by the people that organized what we call the bible today, sometimes in the 4th century AD.
I made an entire thread about the Nag Hammadi Library somewhere here which really clarified for me the deception of the Church, as well as the miraculous way the truth manages to shine through, regardless. Go take a look if anyone is interested. Highly enjoying this thread in the meantime.