215/40 and 215/45 on 7.5et52mm under Day Mouldings. Probably the absolute limit, the front is tight with a wheel alignment for cornering such as 2deg -ve camber. Inner sidewall is ~4mm from a 80mm coil, maybe less at the wing.
The rear (also et52mm) is just as tight when the wheel is close to verticle, about 0.75deg -ve.
944 steel arms rear and 951 stubs at the front. No spacers or apapters.
A wheel this size with et23mm on a stock rear drum will be just as tight, the 205/40 'should' make it easier.
BEWARE! Tyre shoulder sizes are not all the same shape and size for a given tyre size, It depends on the make, more on the original application.
I went from 225/45 F1's on the rear as I had to run ~1.5deg -ve camber, I borrowed a pair of 215/45 Pirelli's (P-zero, I think..) clearance was perfect, So I bought my 215/40 F1's and it was tight again
~6mm difference at the wheel arch.
Matt