@rr3.9 - you are quite right of course, they are the wrong wheels on the Saleen. I have checked with Fly and done some testing myself here at Gaugemaster, and the problem is that none of the wheels - not even the Oreca Viper wheels - are quite right. As you can see, from the side the car looks great with the correct wheels...
but in reality the front axle is now too long and the rear one too short, both due to the different depth that the axle goes into the wheel. Also, on the front, the moulding at the rear of the Viper wheel is longer and so this pushes the wheel away from the chassis because usually the rear of a Sallen wheel is virtually flush with the chassis.
I tried a few varients, but I did not go as far as physically modifying the pieces, although I guess with a little skill you could get the Oreca wheels to fit the front, but you would need a new rear axle as the saleen one is too short (if fitted with Viper wheels) and the Viper one will also be too short, and you still have the Viper rear-of-wheels length to modify too!
Production wise, it is obviously not viable to make a complete set of wheels just for one varient of a model, as the Saleen normally has 5 spoke wheels. Fly apologise, but felt it best and more sensible in this instance to run the model with the incorrect wheel rims.
P.S. Incidentally, the A84 Viper Oreca came with BBS rims, spare parts numbers 79213 and 79214. The A205 Valencia version comes with OZ rims which are Fly part numbers 79215 and 79216.