Jeep: Details of Up Country Suspension package on Grand Cherokee

Hello,
I have a 2000 Grand Cherokee with the Up Country suspension package, and I
am about to buy new shocks for it. From what I can tell there are shocks on
the market that say they are for regular suspension but not for Up Country.
So what is the difference when it comes to shocks? My window sticker for
the vehicle listed the package as containing various skip plates etc, and
"Suspension - Heavy Duty w/ gas shocks". Does the heavy duty mean that it
has different springs than the regular? If there are different spring
rates, then I would suspect that the ideal shock would be tuned differently
than a shock meant for the normal suspension, and might also be sturdier.
O. K. how about dimensions? Does this suspension differ in the dimensions
for shock fitment? If the dimensions are different, then a shock for the
normal suspension might not fit at all or it could fail prematurely due to
being taken beyond its length limits. Does anyone know the details of this
situation.

Thanks for any advice.

Tom