Hi guys, Im new here. Im a woodworking contractor and do a lot of new floors but I have a question for experts on products. I did custom woodwork for a client in a 1850's farm house with pine floors. The floors look ok and do not need refinished, don't think they have enough thickness to be sanded anyway. They have satin oil poly now form when they were done. I want to scuff them down and just put a better looking maintenance coat on but the owner asked if any product out there is much better/stronger that would bond to the old poly. So that is my question, what products are the best for this and any that could be done in 1 coat as a maintenance.

The advantage of re-coating an old floor is you can do it without expensive machinery. The drawback is adhesion of another coat of finish. Wax or other contaminants make it difficult to clean, which is paramount for adhering more finish. It makes sense if the floor may be too thin for another sanding since removing more wood will weaken a single layer of wood as in a lot of old fir or pine floors.
If you like the color when the floor has been wetted with water another coat of water-based poly-urethane will protect the finish that is present if you can get it to stick.
The best technique that I have used is by Basic Coatings, for an old poly coated floor. Look into it. You will need to use IFT, intensive floor treatment. Then rinse off residue with Squeaky Clean, diluted down. Then coat with Tykote. Finishing up with a coat of Street Shoe, gloss of your choice. One coat will protect what is there.This method will not require any sanding or scuffing, but it may need some if you find incrusted hair or other dirt that is in the previous coat.
With all the preparation to make good adhesion you might as well apply two coats at the same time.
A floor polisher with a scrub pad will help remove dirt in deep scratches and a wet and dry vacuum helps with the dirty water and the rinsing with a squeegee. I recommend allowing the floor to dry overnight before attempting to apply Tykote and the a coat of finish. No more than two coats in a day should be applied.