Thanks for the tips, which will be very useful, although it would seem the RSFOURr badge doesn't automatically mean it's a Turbo. I've had a couple of responses from sellers of cars with these badges, where I've enquired if they were also RB25DET and they've actually been NA models. I believe the RSFOUR was offered as both turbo/NA, whilst RWD was also offered with turbo/NA engines.
Off to look at photos of grill's and bumpers....