The Goodyear Eagle F1 Asymmetric 6 and the Michelin Pilot Sport 4 are available at Tyres.co.uk for the Lexus SC430 built after 2003 with standard wheels in the UK. There’s a placard for this on the driver’s door. Check this to see what type of tyre, load index and speed rating it has. This is especially important for older SC430s, as they may have run-flat tyres.
For information on tyre size and cold pressure for the Lexus SC430, check the driver’s side door tyre pressure sticker. Make sure you double check what the tyre sidewall says before ordering. Early models will have run flat tyres. Later models will have standard type tyres.
Since the Lexus SC430 is rear wheel drive, like all RWD cars, not all four tyres need to be the same. Replace tyres in pairs on the same axle, and use the same tyre type and specification on that axle. According to UK safety guidance, you should put the two new tyres on the rear axle.