agree that you need a 0 deg stem 5 deg. i never did like the high riser on retro or modern mtbs. 0 deg always makes a bike more aero stealth looking.
try finding an old skool klein h20 bottle cage. the ringle looks cool but with the klein cage it will be a little more vintage klein l. just personal taste i guess
i say leave the blk tires. no skinwalls.
XTR cranks are waaay cool but can't help thinking what a set of blk vintage cook bros f series cranks would look like...hmmmm.
all in all great build and cool thought process. i myself did a 01 klein adept with a mix of retro and modern parts. so again a modern klein with retro look.