18v+ regulator for 390XP

[shizzzon 461]

Rob told me a while back that i need to pay little extra to have a true 18v regulator installed on my alt.

How much is it for starters and is it still internal i hope?

2nd, for safety sake, i'll have 6 25a stepdowns in the car to run it on 12v still..

But, if i purchase the VCM, can i still safely step the regulator down to ~15v if i ever had to bypass the stepdowns?