well i just did a engien swap from a d15a7 to a d16z6 plus i added a jdm tranny tho but far as what you wanna do to make a d15 to a d16 is change the head from a d16 and put it on the d15 it adds a little more hp but if you want vtec you have to change the ECU also. i like it better that i have a full d16 now its a lot better