Slant 6 automatic to manual swap

I have a 904 with a b&m quicksilver shifter. My car originally was a 3 on the tree and it still has the manual pedal box, but doesn't have the 3 on the tree column. I would like a floor shift rather than the 3 on the tree. The car is a 1963 plymouth valiant with a 1978 225 slant 6. What all will I need? What is a good asking price for a 904 with all the linkages and b&m shifter with less than 10k miles? Is there anyone looking to do a manual to automatic swap who would be willing to do a trade? All input appreciated.