74 Gold Duster and tons of questions

Tanks for the answer. I think you missunderstood 1. and 2. Right now i have only a six cylinder. So i have to get a new engine anyways. It seems that the early 340 is the best choice. I guess With my 6cyl i need a different trans and rearend. Or are they strong enough? My question was, which engine i should get instead of the 6cyl and which other parts i need for this.
So for the sharktoothgrill i need to change the hood, front fenders, filler panel, and bumper. So that way i get a other bumper too. whats different on the front fenders? just the frontpart? but they should bolt right on, right? i guess all those parts bolt right on.