Somebody on here in the last few days was talking about something like that, and how Leupold told them it would be $300. Search on here and try and find it. It wouldn't be replacing the reticle... it would be a whole new scope tube to have their canted illumination turret. I would guess more than $300, but I could be wrong. Check around online and see what your scope could be sold for online used. Then find the cheapest price of the scope you're wanting. I assume you made a mistake when you typed Mk4 M3 3.5 1X40. I'm guessing it's 3.5-14 or something like that?