Is something like this gear ratio/mph calculator what you are looking for?
http://www.andysautosport.com/learni...r/calculators/ As for an LSD on the track I can't comment. I do have a modded M50 with a 4.10lsd. I can imagine for autox it would be alright but would run out of gearing on a track. I'm at 4K roughly at 70.