Is your ke55 originally an auto? If so, the ke55's had a borg warner 35 auto, as opposed to the ke70's, which had the holden trimatic auto box. Not sure if any mods needed for the box to fit into a 55. Tail shaft from the ke70 wont fit your ke55, ke55 one piece shaft, ke70 2 piece shaft. If your ke55 was originally a manual, You will have to custom make a crossmember to change it over to auto. 4K engine will fit, probably best to change over your intake and exhaust manifolds from your old engine and use them on your new one, ke70's have a lot more emission crap opposed to the ke55, unless you have an update 55 which has the same emission stuff and manifolds as the ke70. Also drivers side engine mount is different, that will have to be changed, Hope this helps,
cheers!