I'm getting ready to purchase some of my rear suspension from UPR and one of the things I'm getting is the coilover kit for Strange adjustable shocks (1979-2004 Mustang Maximum Rear Coil Over Kit Silver for Strange Adjustable Shocks - UPR Products). When ordering, you have to indicate your front spring rate (10-125, 10-150, or 10-175). How do I figure that out? I will be doing the front suspension in the spring (k-member, coilovers, etc...) before the Mustang hits the road again, so I want to have the rear set up for that and not the stock suspension. Also, the drivetrain that is in it will eventually be replaced or at least highly modified, so I'm wondering if I have to take that into consideration as well (i.e. weight changes)? Thanks for the info in advance.