I have a 90 suburban with a 4 inch lift. it only has 3 inch blocks in the back with new 4 inch rancho springs in the front. I am going to purchase new rear 4 inch lift 3/4 ton rear springs and I expect it will bring the rear up about 3 inches or maybe more. the rear springs are very weak now and it is about 2 inches lower than level. my question is my drive shave is long enough now. will it still be long enough or will I need to lengthen my rear shaft. just trying to plan ahead. Thanks.