European 126,M110 engine

[mike303]

Hi everybody
I have been visiting this website for some time,great site as usual.I have a 1990,300 SE, european version in need for a tune up and valve stem seals,don't have an owner manual for it,called the dealer up for spark plugs recommendation,explaining that i have a euro model and offering to provide the vin#,but the guy said no need for that,it takes H9DCO.I have read a thread on this forum saying H8dc for european version.
I would like to know if there is any website to pull information about this?.also i want to do a compression test for the engine and would like to know the figure in PSI for the cylinder?.
Tankyou so much in advance and have a good day.
Mike.