My 6.1 retrofit thread
One thing to think about with the piston to valve clearance. The rev limiter only works when accelerating, it will not protect against missed shifts, or bad down shifts. I think one of the reasons you don't hear about a problem with this tight of a clearance is because most of today's cars run with automatic tranny's, so there is some buffer there just from how they work.
Keep up the great work, I am enjoying your project.