To answer a few questions. Yes the car is a 68 B-Body. The 318 is already in the car so no cost there. I also have a 400 laying around already with a 727.

To answer the question on the gears I have thought about 3.23s for the car but, I do like the 2.76 gears as I do have a lot of highway to travel here locally. Most of my driving is done between 55-65 mph.

As far as mileage is concerned I do put a lot of miles on the car and while it's not a huge concern I also kind of want to have my cake so to speak and I do plan driving the car cross country a few times or so I hope in my life. Hopefully that answers a few questions.