Frank,
Mex really knows his stuff.
I have a 2019 350 Diesel.
There are two batteries, 12 volts in parallel. the Negatives are to the frame and the positives are cross connected together forming one larger 12volt battery.
I've been looking into replacing both of my grounds because they appear to be undersized for the load I'm placing on the cables (number of amps observed when cranking is right at the upper limit for the size of the cables).
if you want to use the ground of the chassis - make sure both of your existing cables are in excellent shape - are clean, and there's no corrosion. Slather them with silicone grease to insure no corrosion.
You'll need to run 1 00 cable to the location of the winch with an inline fuse rated at 430amps (or as close to it you can get).
You'll probably get better performance if you run both a positive and negative cable - but it'll work using the frame as a ground.
josh