I have a 1983 Honda shadow and it needs new front brakes. Can I just use any brakes and they will fit? I ll need the whole system

I have a 1983 Honda shadow and it needs new front brakes. Can I just use any brakes and they will fit? I ll need the whole system - 1

No, because the brake calibre bolts will be in a different position. Some other Honda bike parts may fit as they were common to each other, such as wheels and brakes from a CB400 fitted to the CB650Z, but you will need to investigate which other models use the same calibres, if any.
My best advice is to fit proper Shadow parts and not cut corners. We only get one life so take care.

You can use different manufacture's brake pads
You do not have to use Honda brand name parts.
But the bake pads have to say on the package that they will fit your
exact make, model and year bike.
Brakes that are used on Harley Davidson motorcycles will not
fit on your bike.

Just like windshield wipers for automobiles, you can't just use any wipers and they will fit.
They have to be made for each specific auto.

Although you can make plates to accommodate another caliper it is easier to start with one that has the the centres of the bolts in the same position and that use a disc of a similar diameter (otherwise you might face clearance issues). Because the bore of the master cylinder is critical it is worth getting that from the same source as the caliper.

I'm sure that there have been many conversions of Honda Shadows, I would look into owner's forums and find out if anyone has uprated/exchanged brakes and what was required.

If it involves making plates do not just eyeball them or make them out of a bit of scrap - these are critical because they will take quite an amount of force, you do not want them to buckle.

I highly suggest taking your bike to a reputable shop.

"Can I just use any brakes and they will fit?"
No and no.

"I ll need the whole system?"
And you'll need the setup that is specifically for your make, model and year of bike. Nothing else will fit.

No, you can only use brake pads made to fit that bike.

You might only need break pads. Auto parts store will have them for less than the dealer. Go to you tube and some body will have a movie on how to do it.