This is my 1970 f100 4X4. It was my daily driver forever, and I restored it once along the way. I parked it about 12 years ago when I needed a bigger truck. Now I want to bring it back to life again with my oldest son for him to drive when he is 16. But I want to swap in a more fuel efficient driveline, so he can afford to drive it. It weighs around 4000 pounds and came stock with I think 170 hp? (360 fe V8) So I think weight wise it would be similar to an SUV or a Dodge Dakota/Toyota T100. It has a cavernous engine bay, so pretty much anything would be lost in there. I would want to keep things stock so the original 360 can go back in one day. Any suggestions?