60yds is quite a long poke. I'd look into testing Hevi-shot and Wingmaster HD in 3" minimum, 3.5" if you want to spend the $$. No. 4 shot will carry more energy downrange than no.6, but your really need to pattern yoru gun at that distance. At long ranges, pattern density will be a important factor. Remington makes a duplex load with no 4 and no.6 shot.
Try to find a load in the biggest legal shot size. In most states, this is no.4. In many states legal shot sizes for spring turkey are 4,5 or 6.