Don't remember the price on the running boards, maybe $120ish. the extention was a labor of love. I did another 9 for my brother, stock tunnel wide boards and smooth top. Mounted the stock cooler underneath on some spacers. Also added to the edge cooler and radiused in under the tunnel top.
Went with the aero for simplicity, I can take it with and throw on any thing else. The 66 made for a easy and simple install. No tank, no pump, universal mounting, spool speed and didn't think the extra power on the auto would be worth the weight and hastle. I live in Western Washington and there are not the big wide open spaces and hills that make a auto type shine.
Did some research and used the biggest 66 witch is 66 224-300. As for the big boost Nitros !st season with them. But at those boost levels I am sur I will need some binoculars.
The price of the system was not that bad. I have about $3500 in it. I do however own a machine shop and this makes it easier for me than others.
I would recomend not to be afraid to tackle this If you have some skill and mechanical ability. I would be happy to help anyone to build their own kit