ready to order valves from SI your only option is Stock sizing.
unless you know exactly what size of valve you need depending on the engines specifics the amount of power its putting out, the desired rpm. power adder. ect .. or youve gone through and did dyno testing to prove that yes this exact size is going to actually help your engine breath for X amount of CFM at this lift., not make less hp, well then, dont just guess a size.
if you dont know specifically that you need X.XX size then your best just going with stock.