You didn't say if this is a stock frame. If it is , you need to strengthen the frame by boxing it. Then you have to figure out what rear you want to use. Then ,type of suspension ,front and rear. The frame has to be the first thing you do. Once that is done, then you can continue with motor & trans. With the motor & trans you will have to also decide what motor you want to run, Chevy,Ford or Mopar. Then figuring out how to mount them is the next thing.
You seem to be a novice at this and with all the fabrication this may need, you may want to have someone who can TIG weld and know how to do the things I mentioned.