I thought I would chime in on this. My engine is an 8k RPM 340.
I would call it an old school build that relies on high RPM and high compression to make up for it's lack of cubic inches. It was a very expensive build with all the precision machining coupled with the cost of all the quality valve train components.
Now when we talk reliability we need to put things into perspective
My engine is/has been very reliable but you need to realize that reliability and long life are not the same thing.
The high spring pressures and stress at 8000 rpm limit lifespan on some components.
So, reliability?
Sure as long as you are replacing springs and pulling bearings every 2-5 thousand miles.
In other words
. Things that are not standard maintenance items on an engine that only turns 6-6500, become standard maintenance items on an engine that turns 8k+.