No long valve or anything special needs when you modify a Vortec head for lift past the .480 mark.
Most will work just fine to .500 lift. (from what i have seen)
All you need is a cutter to lower the valve seal.
You remove the valves & valve springs.
Cut the top of the valve guide down and install valve seals.
By cutting the valve guide down you increase clearance between the valve seal/guide and the valve spring retainer.
Illustration "B" is the area that needs more clearance.
I do this and charge 75.00 plus price of seals. I also check valve seat angles and lap the valves in.