Clueless in Texas

I have been considering building a powered scow type barge 40'x12'x4' to haul equipment. The weight of the boat will be 5000lbs with the cargo also at 5000lbs. I need enough HP to push thing thing 10-15mph due to long runs. I have been told that it will take in excess of 500hp to acheive this. I have also been told that barge designs are very inefficient. Now I have a new idea. I am considering building a mini tug, the Sherwood Queen designed by Glen L. and installing either a Chevy 350 or 454 (don't know if this fesable for boat design) and then purchasing a 40' Laffite skiff and modifing it to serve as the barge. My questions are this.
1)Is a Laffite skiff hull design more efficent than a scow barge.
2)Will 250-300hp be enough to push this 10-15mph.
3) Based on the Sherwood Queen design can I install a motor this big ( the tug deminsions can be veiwed at Glen-L.com.)
4) Am I just crazy.

Thanks

 

These guys have already built some boats similar to what you need, and a lot faster on less hp, to boot:

http://www.winninghoff.com/

 

Thanks for the lead. I think I have already spoke to these guys. They quoted me $105,000 for such a beast.

Thanks