Re: Correct Bilstein rear shock PN for lowered syclone?
Bilstein doesn't make lowered shocks.
Dropping the rear with "blocks" you're correct doesn't change the suspension travel, it only moves the axle up (closer to the fender well) so you can run stock length shocks, but you can also run lowered shocks if desired. Depending on the size block used you may want to trim or change the bump stop to help avoid a harsh ride.
Dropping the rear with "lowered" or de-arched leaf springs does indeed reduce the amount of suspension travel and I would recommend getting lowered shocks.
Personally I've never been happy with the lowered shocks that Bell Tech sells. I've put them on many vehicles and always felt them to be too soft, but that's personal opinion.