The 3/4 combo is the lowest Ruger offers, they list that pair as "Low" on the ring selector chart on shopruger.com. - it says 32mm bell but that will take a 40mm as long as it's not pushed way to the rear. I've never bought anybody else's rings so wouldn't know if Leupold or someone might offer something a tad lower. The 4 goes on the rear bridge since it is lower than the receiver ring and I've never had any interference with any standard scope ocular bell using the Ruger factory rings since most scope oculars are all a standard size no matter the objective size. Ruger does offer 30mm rings as well in a "Medium" 4/5 pair - I had called the 4/5 "high" in my previous post so my bad on that.
I've bought 7 Hawkeyes over the past several few years and just automatically swap the 5 for a 4. The 3/4 Low pair works for any 1" scope one is liable to use with a hunting type rifle - straight 4 or 6x, 3-9x40, even an old long Leupold 12x40 I use for load workup. Unless a scope has very short eye relief a 40mm bell generally ends up with about 1/8" or so clearance above the barrel, even on a magnum contour.
Ring selector chart 
