After many months of searching here's what I came up with for my needs. I have a :http://www.kingcanada.com/Products.htm?ID=11890
I need to make it sound like a 1000W Honda.
suitable crate from a manufacturing company $25.00
obtained damaged acoustic tile from work and a local company for free
Utility Exhaust Fan UF10-G 10" fan (120 Volt, 10 foot cord - Removes air in a 10' x 10' room every 2.5 minutes - providing adequate air inlet is available) for $49.99 +taxes
2 metal dryer inlets with screens ($8.99 @ the Home Depot)
external electrical outlet with weather proof cover (I had left over wire and a duplex)
I lined the box with the acoustic tile using builders glue
I had a friend weld an extension onto the muffler pipe so it exhausted directly out of the box
installed the utility fan near the muffler/heat shield (I finally figured out that some hot air blows off of the motor heating up the inside)
I installed the 2 dryer vents for cool air intake.
Some original ideas I tried were a 15cfm bath fan exhausting outside. The box became so hot the gas in the tank started boiling out of it. I tried the same set up but bought a longer gas line and bolted the gas tank to the top of the boxes lid. The results were internal box temps >120F. When the utility fan was suggested, and placing it right near the heat shield/muffler the temp never got above 90F. I also had to cut a 4" * 4" hole for additional air intake.
If I had to do it all over again, I'd cut a strip the entire from of the box near the bottom 2" high for air intake and forget the dryer vents. That way there's front to back air flow. The final result is here:http://fishtank.uwaterloo.ca/~spaterso/generator-1.jpghttp://fishtank.uwaterloo.ca/~spaterso/generator-2.jpghttp://fishtank.uwaterloo.ca/~spaterso/generator-3.jpg