Shock Absorbers / Dampers
Once you have your ride height sorted with suitable springs you can start looking at shock absorbers that match them.
You need dampers to control the springs on rebound and also to assist the springs when you hit a big hole and they are under compression.
Under compression you want a shock absorber that is stiff enough to prevent the spring collapsing too quickly but has enough give to give a reasonable ride, allowing the spring to do it's work in getting the vehicle back up to ride height again.
On rebound the damper needs to prevent the spring expanding too quickly and launching the vehicle into the air. This also serves to prevent the spring over extending on rebound and basically bouncing up and down.
Most cheap shock absorbers are mediocre at both tasks meaning that when you hit something hard, like a deep hole at any speed, the front end will bottom out, transferring all the shock into the occupants and the vehicle and often leading to a dead stop. You can mitigate this to an extent by fitting two cheap shock absorbers on each corner.
On rebound cheap shocks rarely do a decent job and this can lead, particularly on the back end, the vehicle kicking up in the air. On a washboard surface at speed the lack of rebound damping combined with poor compression damping can lead to the vehicle nose diving into the ground and flipping end over end.
I've tried a number of different makes/models of shock absorbers including ProComp, Lovells, OME, Bilstein and Koni. the first three and also Terrafirma) are pretty mediocre at best on both compression and rebound and have to be doubled up to give anything like a decent result.
Bilstein, I know Matthew will disagree with me here
, I find good on rebound but pants on compression because to get decent rebound they are far too stiff on compression giving a really harsh ride - so harsh you sometimes feel like they've been replaced with angle iron !
Koni are the best I've found so far and are now standard fitment on the "White family fleet". The Koni Heavy Track has adjustable rebound and gives a good but controlled compression. They're also reasonably well priced for a good shock absorber. At around £60+VAT each from Paddocks they're pretty hard to beat as IMV they give excellent performance without breaking the bank. The next step up would be Fox or similar but then you'd blow almost your entire budget on one corner !
Koni do a Heavy Track Raid version which is a lot more spendy than the normal Heavy Track and isn't worth the extra unless you're planning on a quick high speed run across the sahara any time soon.
Mounts and lengths for the shock will depend on the spring and suspension arm setup but remember that every time you get a longer travel shock it won't compress as much so needs to be mounted differently to get the extra travel. Sometimes a "standard" length shock will give you all the travel you need if it's correctly mounted.