Not sure of the offset of the enkei 15 x 9's but they fit under std arch perfect with 225 50 15 tyres with 2 1/4 springs, the 8 x 15 don't fit proper cause they have the wrong offset.
Sorry but that is a generalisation
...I have 8x15 enkei that will fit
The issue isn't 8 or 9j but all about offset as I can show you 7j wheels that will not fit because they have extreme negative offset.
The way I see it is if someone has managed to fit 8j zero offset with 205 rubber and have no issues' then the 9j will sit 1/2 prouder on each end. Is there 1/2" back spacing left to accommodate deeper wheel? On non zed datuns that have IRS one has to notch the trailing arm by a few mm if using 9j zero offset or use 3mm spacer.
On the arch side will this extra 1/2" make a difference given that the tyre section will till be 205 and hence stretch inwards as it approaches the thread? Are you willing to roll the arches if need be or use rock hard suspension that limits travel?
I have a set of 8x15 with -ve 15 or is it 20 offset with 195/50/15 rubber if you want to test once you done the math on how close these are to your desired wheel. I m not a million miles away