Running on wide modern road or race tires would completely change the expirience, you'd loose the natural four wheel drifiting and the car would handle like a very badly setup Formula Ford, if you want to drive historic single seaters GPL really is the only place to do it. I think with a large amount of work LFS could just about pass off cars back to the 70s where a lot of the major changes took place in terms of basic concepts and materials.
I don't think it can be said that a physics engine can be made to suit any car by entering in a few parameters, LFS has been programed for modern tires and suspension systems and materials. The chances of a BRM V16 and Morgan's trademark sliding pilar suspension magically popping up from LFS tweak are about as likely as Eric getting a liscence and building the 'ring along with authentic Castrol R (I'd be happy to be proved wrong )