NEW TO LOWERED DUALLY WORLD

i HAVE THIS 97 F350 STOCK, BEEN POKING AROUND THE SITE FOR A COUPLE HOURS, 1st thing i have learned is there is a lot of chevy guys here!! love the chevy, got a GREAT deal on the ford so i went with it. Anyway, I want to lower it, after reading threw here i am getting that a 3/5 seems to be the best way to go with the ford, my biggest question is do i stay with the stock 16 rims, or do i go with some 19.5? i got a sweet deal on 19.5 rims and 225/70 tires so i bought them based off of limited knowlage, and a very fast internet search. i put the pic of the slammed dually that i am now sure that it has same rims i do, so i am guessing that it just has lower profile tires. any help would be AWESOME!!!