can some one help my engine

[monkeys gt]

ok i have a 2000 mustang gt and it has a tick witch i think is in the valve train and i was hopping if some one could tell me if it was possible to pull out my stock 2 valve 4.6 sohc and replace it with a 4 valve 4.6 dohc i know i would have to change the ecu and all so i was going to order one of the ford racing crate motors because they come with all of the wire so if this is possible could some one tell me how hard this would be thank you