with everyting else being the same what should i pick up in speed time ect?

Depends on how many lbs your stock track is. Less rotational weight=more hp. I forgot the rule of thumb, somthing like 7lbs rotational weight = 1 hp?????

In 500` its a tenth.

it will make a huge difference. not only is it lighter but it also has shorter lugs for less resistance and also you should be able to run shorter studs wich again means less weight and will bite better in the ice. on average for top end or radar running depending on set ups should net you 5-10mph.