I see they have several different models- D450, D452, D453, etc However, their web site doesn't do the best job explaining the differences unless you call up each of them and look at every line. Has anyone already done this research and care to share? On the TTI site, you plug in info and it lists the results with highlights of the application. This cuts down on a lot of the leg work. Doug's didn't even return results for my 73 Satellite, other than with a 5.7!! Thanks in advance.