Rails for Proliant 6400R...

Hi all.. I finally obtained (for free no less) a 19" (slightly higher than
waist high) rack mount cabinet from someone that left at the curb
over the weekend (for vultures like me) and would like to put my Proliant
into it at some point.. My machine currently has the internal rails (the
side that mounts on the chassis) but that leaves the other half that mounts
to the rack..

So, I was just wondering if there's anything special I should know
about the rails for these machines (weight requirement,etc) and
can I just find some on e*bay that are for any Proliant (e.g. are they
all the same)?

TIA!

-- Rick