Replacing RC 2.0 with Bilshtein 5100

I'm on 4.5" RC lift kit with 2.0 shocks, they are very stiff on trail and I feel the jeep falling apart.
After reading some post seems the 5100 bilshtein are the favorite of most trail riders.
I intend to install IRO long arm upgrade in the future so which ones should I buy. Parts numbers is needed.
Thank you

Best way to do it is after your done your suspension measure your extended and collapsed lengths by flexing it out without any shocks.

Is your sway bar disconnected or your rear shackles at a bad angle or seized? I hate to say anything good about the RC stuff because it requires constant maintenance and replacement of the ends, but the ride is really good. Only time anyone ever complained about it being harsh was when I didn't feel like airing down, left the sway bar connected or had stock shackles that wouldn't actually flex.

Bilstein listed for 5-6" lift are:

front collapsed - 16.9"
front open - 28.4"

rear collapsed - 15.9"
rear open - 25.9"

http://www.4x4groupbuy.com/store/bilstein-5100-shocks-jeep-lift-p-48700.html

Yes best price I found was at 4x4groupbuy