i have an 81 with nice carpet and mats that i believe are original. a good shampoo is due soon. what do you guys use and what technique? i dont want to blast it with harsh stuff , but i feel it can be "brightened" up

Have used a regular carpet cleaner with upholstery attachments with some success.  But prefer to take the carpeting out of the car, hose it down, really scrub it good and hose it down again.  Then let it completely dry in the sunshine before putting it back in the car.