i need rings fomr my remington 700 SPS Varmint with the bull barrel. i got a 2 piece weaver style base on it. what height rings do i need for a 40mm objective scope??? either the 4-12x40 that came with it or a 3-9x40 leupold vari-x II i have...theres no rear sight or anything in the way..what do you guys suggest?? thanx alot