Diesel Bombers - New and way over my head (for now)

Hey everybody, my name is Alan and I a member of the 101st Airborne serving in Ft Campbell KY. I am about to head back over to Afghanistan and want to spend the next 9 plus months researching and picking your brains on a project I have going.

First my experience - very little. I owned a 2003 6.0L (I will post pics after I get this cookin') and I feel like I built it right for my needs. Mostly looks I have to be honest in that I lifted it up - made it look cool but left the engine pretty much alone except for minor upgrades, but that is all I wanted and didn't want to mess with reliability.

Now...my project....and this is where I will need your help. I am building a project called the MRAT. A play on the term MRAP and Rat Rod. Please be clear that it will not be a "rat rod" in the sense of many of the hunks of garbage we see on the internet. I simply apply it here because it is a hodge-podge of different parts and not meant to look like a fancy street rod.
It is a 31 Buick (think of a big Model A sedan) that I am making to look like a MRAP - in this case a mix between a MATV and a MaxxPro - similar to what I commanded in Afghanistan. You see, I owe my life to these vehicles and those who designed and built them. As the weapons squad leader of my platoon, it was my job to run point on missions. I have a knack for picking good routes both in terms of making life tough on the enemy and I was normally able to keep us from getting stuck. Where I operated the term "road" referred to any three or more motorcycle tracks. Basically it was ALL offroad driving and that is not easy to do with a 15+ ton truck made for the roads of Iraq...but she did it. I took my MaxxPro to places the engineers never imagined she could go. I sent to big truck heaven after hitting two...ummmmmmm BIG.....IED's and two took the lickin' and kept on tickin.':bat:
I actually have the blast scarred International emblem from my last one and that is going to be mount on the dash. I hope this helps anyone reading this long winded mess the inspiration for the car. There is a lot more to this, but I will save that for another time.

Okay....so why do I need help? Well...it's the entire powertrain.

I am using a DT466 for the engine. It is the old mechanical version not the DT466e. I did that because I wanted to stick to the RAT theme of low brow parts.

I also have an Allison 545 that I am told should mount up to it fine. Is that true? Is the 545stout enough? My plan was to get it all togther and running (stock power output) and once I get that dump some real power into it. How much can the 545 handle? Can it be beefed up? Is there a better choice? I plan to drive this vehicle long distances, so I don't know that I will ever go too high on the HP, but I am curious how high I can go and maintain some sort of reliability? There simply isn't the same level of aftermarket support for the DT466 as the cummins etc have.

I really need your help guys/gals and I know there are folks out there with mountains of knowledge, so dump it on me. I gotta learn and I gotta learn fast. When I get back I am going to dive into this thing and hopefully get it on the road before winter '14.

Thanks in advance! I have been a diesel fan for years and this is my first big project, so I am really glad I found this site!

Alan