318 head swap......how to?

I just got a performer intake from member jason69r. and my valve seals have just started to go out. the car smokes only on startup, so that is what i am guessing that it is. i am thinking about finding some 302 casting heads and putting them on my dart. i was just wondering what thickness head gasket and what brand will i need. also, what work should i get done to the heads? i am doing all of this because i am planning on installing nitrous on the dart and want everything to be right before i do so. do i need any special new bolts or anything like that? just what should i get before hand so that the job can be done in a weekend because i have to drive the car to work during the week.

thanks for the advice,
daryl