Where are you getting 400lbs or 500lbs from with regard to shocks? Also, for choice of shocks, what kind of ride are you looking for - stock ride, sportier handling, all out performance handling?
If money is no problem, the adjustable hydraulic shocks from QA1 or Viking are very good and can be dialed in for your desired ride requirements.
If you're on a budget and looking for a good shock for a cruiser, Monroe makes shocks that provide the original ride quality. For gas shocks, the KYB Excel-G is a good choice, while the KYB Gas-A-Just provides a much stiffer ride. For another gas shock option, Open Tracker Racing sells a Bilstein Street shock that has good reviews.
If you're looking for springs I recommend Eaton Detroit Spring. Give us a little more detail on your question and more members will chime in.