I've replaced many wings on 75's over the years and there are always washers under the top rail. It's perfectly acceptable on a car like the 75/ZT to do this, to achieve perfect final alignment of the panel - the shell of a 75 is incredibly accurate, but there will always be tiny differences between individual cars and panels, which can be rectified by inserting or removing the washers which act like shims.
Hence, add or remove as required on your car to get the best fit against the bonnet edge, and compare to the other side to ensure they match.
Lastly, DO NOT add silicone to this joint !!
There is no reason to seal it as, unlike an old Metro, you have a plastic wheelarch liner which stops the mud & muck collecting. Silicone is for sealing around baths, not for fitting 75 wings.... If it were meant to be used anywhere on our cars, Rover would have done so during production and as I've never seen a rusty wing top on a 75, it certainly won't aid corrosion protection ! It'll just squeeze out around the edges and anyone looking under the bonnet will see the signs of an amateur bodge.
Equally, there is no sealer down the rear edge as the wing is simply bolted to the A-pillar, with a vertical piece of foam in a plastic bag pushed in from the wheel side once fitted, to fill the void. Be careful though, as these can trap moisture and are questionable against any noise saving they provide. So up to you whether you refit or not.
Good luck with the alignment
