Now that's an interesting thing to say as my Brother informs me it even makes a difference to value of an E type if you don't use the correct bolts i.e. the original manufaturer.
Well only if you are building one of the early "Outside Locker" cars.
This is my car which I restored but used top quality Stainless where safe....But then it's not a standard car now.
http://etypeuk.com/carsales/showroom/view/Jaguar--E-Type-Series-1-4.2-40.html