Forester engines

Hi there 

please can you advise , i have a 1997 Forester ( Auto) with an EJ20 Turbo engine . It has the coil pack on the top of the engine , with 4 plug leads going to the plugs . My question is ....... Th motor produced a Knock , so need to replace it , i have the availability of buying a second hand Jap engine in South Africa , for a lot less than an engine rebuild . How different are the engines from one and another 

the ones i can get hold of are EJ20 Turbo engines , but have Coil on Plug heads 

will i not just be able to remove these , and use my original coil pack 

what are the major differences that i need to look out for , and what problems might i encounter

Thanks in Advance 

regards , Clyde