Converting manual to auto in a XM
G'day, I have a newly renovated 1964 XM Falcon with a 170 Ci motor. I would like to change the existing 3 on the tree manual to a floor shift 3 speed auto. I was told the C9 would be the best choice. Would this bolt straight onto my engine and would I need to do any modifications to the transmission tunnel and firewall as someone told me that my transmission tunnel looked too small to take an auto. But surely as I know the next model XP came witha c4 they wouldn't of increased the floor pan. What other parts would I need or is there a conversion kit.