need info on building a Big Block for towing

[spinning wheels]

I have read many post in this message board on how to build a 383 stroker small block. What I need to know, is how to build a Big Block (454) for towing. I have found a donor, its a 1 ton ('85) GMC flatbed. The truck is beat, but the mechanic at work tells me that the motor is strong. I will still go through the motor. Its got a turbo 400 in it also. I will take the motor and trans and part the rest. My 3/4 ton has the stock 350/350 set up and when towing, she is wheezing real bad. Not to mention using a quart of oil in a 60 mile tow trip, and getting 7 mpg, and loosing half a gallon of water. So either way, she needs a boost under the hood. Thanks in advance for all your opinions and advise.