I presume you are running a naturally aspirated 4D55. Shifting over to a 4D56, an intercooled turbo version, should make the world of a difference. 4M40....the engine fitting is not meddlesome but the gearbox is much larger and would need lots of cutting/welding....and the engine gearbox price would be another killer....so stay away from it. But if money is no major consideration and you really want to fly to surprise some of those stiff necked 1 KZ owners, go for a 4D56....the twin cam EFI version or the V6 6G72..... that'll be money well spent!!!