motor mod ?

[quadrider60]

im rebuilding my 01 400ex from the ground up and its getting close to doing the engine i just need a little help choosing what i should do i was thinking
416 bore
port and polish
had valve springs
hot cam
k&n filter
hmf exhaust

or a 426 with the same mods. and how do u guys think a motor like either of those would hold up to a stock 450r

[duke416ex]

I would go with a 416 and then later you can do a 426 if you need another bore. I would get the crf450 timing chain and think about a different carb. That set up should hold a stock 450.