There are many front seat configurations. Civil and Military and I'm sure some of the foreign manufacturers used their own seats. I've seen the Hard Armored seats from US Army contracts and flown some. Some of these were in USMC versions. The UH-1E's that I flew had those, and some had the civil web seats and some were an aluminum "bucket" with cushions (those were the hardest seats I've ever sat in). The UH-1N has a completely different kevlar framed seat with the mesh webbing velcro'ed in (I have never seen these replicated in any kit). The seatbelts were bolted to the frame not the floor, at least originally. It was found that in accidents, the front seats exited the aircraft through the windshield. But that was at a Gazillion G's, so it really didn't matter.
So the bottom line is that there probably are MORE versions of seats than are replicated by model companies. You having seen several that were most likely valid variations. So you can feel comfortable putting them in, unless you are following photo documentation.
HTH
Steve H.