Wilcox mounts or replica mounts are the way to go for a SEAL kit build if you're interested in making a SEAL load-out..etc.
If you're interested in building a SEAL type kit, there are great looking and very functional metal Wilcox replica mounts (with trademarks) on-line and on e-bay.
Basic SEAL impression MK18 MOD0 air-soft rifle:
Obtain a replica LMT SOPMOD Crane stock then strap a semi-wide tan rubber band around the stock latch to keep the latch from moving..etc (mainly just for looks in air-softing to add to the SEAL impression)
Obtain a SOPMOD/Block 1 or 2 based M4 CQB-R, 10.5" barreled AEG or GBB rifle with Colt or LMT trademarks on it and with a KAC replica RIS
Obtain a replica Wilcox mount for Aimpoint scopes (the M2 is what I would use for a MK18 MOD0 rifle build for a SEAL kit)
Obtain a rear replica LMT BUIS (Back-Up Iron Site)
Obtain a replica LMT sling attachment
I'll list more items for this impression if needed...here's a guy that put together a real one that is a darned good example of one as far as I can tell. Just follow what he did but with replica parts for your air-soft build...
http://assassin.wordpress.com/2006/08/2 ... completed/