I am looking at getting new tires for my 45 but I am not sure what size. I would like to get R4 tires and I know what size the book says but I am wondering if I can put a 43 x 16.00-20 on the rear and a 28 x 8.50-15 on the front? Why..... because a guy down the road has a brand new set of Titans for sale with wheels for $750. Will these work on my tractor?