To get the heavy duty parts, look under the circle track catagory. The 6T(part no.6400) has all the tougher components, and has mounting dampers. To get the built in rev control, try the 6ALN(part no. 6430). Also has weather tight electrical connections.
No, I don't work for MSD, but have dealt with them for years. They have great products, and stand behind them 100%. There was a post earlier about some people's experiences with them, and they were all very positive. The key is matching the product for your particular requirements, and following the directions closely. As they say, it's all in the details....
Dave
