For one thing a clamp neck and new bolt are basically pointless upgrades. If you want to upgrade your Rodeo to tournament grade you need to add some better things than that.
HPA is high pressure air (AKA nitro). A BKO will need HPA or a good reg for CO2 (ie: Stabilizer) and an anti-siphoned tank.
A 45/3000 tank will get ~450 shots. On a BKO it should get a lot more though since they are very efficient guns.