Hippslsvtec18

Ok well heres my setup so far i have a D15 B8 bottem end thats at the machine shop getting decked cleaned and bored to 75.50mm so i bought new 20 over pistons and im stuck with what rods to go for i will be using a z6 head what rods should i use for this setup i dont know if the rod length is going to effect me in any way an i want to have a successful build so any help would be greatly appriciated thanks