Lunar caravan octagon shock Absorbers

[Lyndon64]

I have a Lunar solar eclipse 615 twin wheel ,i want to fit alko octagon shock absorbers to my van ,looked underneath van got the 3 holes in chassis but cant find the rubber bung on swing arm ,alko say they can be fitted to retro vans with alko chassis 1994 HELP PLEZ

 

[Sproket]

Watch this video on how to fit them