Well SAE or DIN as far as what I can recall as I
can't seem to remember what they stand for exactly at this moment is SAE is at the Flywheel as rated on an engine Dyno and is usually called advertised horsepower hence the I D plate on
your car. These are not always true! The other rating that I am used to hearing about is the at the wheels horse power rating .
The premis of no water or oil pump is one that I'll have to ask a friend about as he will know for sure so I'll get back to you on any of that stuff.
The S I model you're discribing sounds a lot like
the GX version . The double valve spring set up is usually a sign of a taller and longer duration cam shaft and would definetly mean more than usual horsepower and torque .I am anxious
to see
some photos and hear more about what sounds like a rare model . Good find Guys !
C-Ya Steve