jack c

Hi, first post so hello all. Just bought myself a little DT125 to rebuild as its a bit tatty, its a 1990 H-reg. With the bike I got a spare engine thrown in but its from a 2002 bike. Will the engine fit stright in? And will the parts be interchangable? The other question was the later engine has the power valve assembly and control unit still conected and I want to use that on the bike but i have noticed that the connections for the control unit are different. Would it be possible to buy a wiring harness from a later DT and fit it to my bike? Would i also need to buy a CDI unit for this? Or would it be easier to get a control unit which fits the existing harness? Thanks