why is it more correctly called a 450 ?
Because it probably has the 4.5 lt engine and the automatic three speed. I have gone through the European and the US spring specs and the European models have tauter springs. The 3.5 in the euro models has higher compression and I think it weighs less. The reason I prefer the US 350 over the 450 is because most of the later 450's had power windows, climate control, ugly bumpers and a few other doodads to break.