I bought a series/defender snorkle off ebay for £60,
I curved the plate that usually fits onto the series/defender air intake hole,
curved it to fit onto the side of the scuttle board,
Drilled a hole through the scuttle board,
then fitted flexi-pipe from the air box, through the scuttle board, and fitted it to the inside of the plate.
All the other fittings for the clamping of the snorkle fitted the RRC O.K.
I hope this helps.
Not cheap cheap but a lot cheaper than buying a Mantec or Southdown.
Photos available if you pm me.
Cheers......