I would stick with the GP4. Although the 280 could probably handle the front, it wears very strangely and very quickly from the brakes and usually needs replacement sooner than the tougher GP4. Since you're heavier and touring is heavier, that will work your front brake a lot.
Originally Posted by
Panthers007
I've heard* that "spoke-prep" tends to act like Loc-Tite. You don't want that as you want to be able to true the wheels later on if they need such.
Spoke Prep is different than Loc-Tite in that it is more brittle and breaks up when you try to retrue the wheels. I have never had any trouble working on my 14 year old wheels which have Spoke Prep.