jayber

400hp on a 302 without power adder is a tough order to fill and be streetable! Doing it without MAF and expecting it to idle is damn near impossible. Going to take alot of cam in NA form to make 400hp. Why even bother building a motor you will hate? HP in a truck isnt going to be fun as you think.
As someone suggested 460 torque is what your wanting. You can build a mild 460 that will idle smooth as a Lincoln and on the hammer you will get the smile you are looking for. Dont tie your own hands Good luck

Marklite

351", all the way, stronger bottom end.

Execut1ve

I looked into a 460 very briefly, before determining that for my goals the 351 was probably better due to the better pricing and availability of parts. I'm really not looking for anything crazy or "fast," just want to feel strong driving around town and be able to tow/haul without straining too much. I recently pulled a small camper through the KY mountains and I had to downshift frequently and made liberal use of the climbing lane.

It's seems pretty clear that the 351 is by far the better starting point than the 302.

qdeezie

If I were building a 351, I'd keep my build very simple. 1) Edelbrock upper and lower intake, 2) Aluminum Heads - Trick Flow 170, AFR 165 or Brodix ST 5.0 heads and 3) Custom cam.

If I were building a 408, I'd definitely go bigger on the heads and get the lower Edelbrock ported to match the intake ports on that larger head. The head size would be 205cc head at least.

That's my .02 on a "proper" 351 setup.