I ran a K3500 with a TBI 454/400 with 40" boggers ad 3.73s. Going around a corner would lite the tires up But a good rule of thumb for tire size/gear ratio, take the size of tire your going with, divide by current tire size, multiply by current gear ratio. But always round up. If future tire size is 35s, current is 31s, and ratio is 3.73s, comes out to 4.21 or something. But because of the extra weight and rotating mass of larger tires, 4.56s would be the best bet. Big blocks are lil different since they have more torque than a small block. My old man had a 98 with 454/4l80, and with 35s and 3.73 gears, it pulled em great.