Welcome Willem - my 69 280 SL had been imported from the US maybe 20 years ago and the only modification I am aware of was a KPH speedometer. US lights, bumper overriders, side marker lights, everything was left alone. Don't know about seat belts and smog requirements (mine had neither) plus the requirements may have changed in the meantime. I suggest you just give them a call, I'm sure they've seen many a Pagoda come through from the US.
Hartelijke groet, en veel plezier met je Pagode!