I think the engine code is behind the bypass hose at the top of the engine. I've never got an eyeball near it, so, look in the boot, on the floor near the threshold should be a white paper sticker, it will give the engine, gearbox and paint codes. Pukka GTD's have the RA engine early on, SB later. Sorry, I don't know when the changeover was. my GTD's are an "H" plate and a "J" plate, both SB's.