The 911-16 Comp spring will work great.
checking guide to retainer=go to the hardware store, the spring section and get 2 light springs that fit the retainer and spring seat. install them and measure at full valve lift.
checking valve spring bind=stick spring in vise, clamp it to the measures lift and measure between coils.
by the way , those stock rocker arms will be anywhere between 1.35 and 1.45 ratio.