Where to connect winch positive

[SierraHawk]

5.4 here. Thanks

[unreng]

Don't touch the positive cable to the frame.
One thing to consider is the wire gauge of stock ford diesels...it's not optimal.
A winch should be wired directly to a battery, but there are alternatives...like using the jump start post.

The jump start post on the frame could be used, just make sure the wire from the post to the battery is properly sized.
Also consider that a winch pulls significantly more amps at the upper limit of it's range.
The Comeup 12.5 winch mentioned above pulls 470amps at 12,500 lbs and 300amps at 8,000 lbs.
The Smittybilt 12k comp pulls 375apms at 12,000 lbs and 300amps at 9,000 lbs.

Starting at the frame-rail batteries and wiring to the back of a van is at least a 10-foot round-trip.
That's a 4/0 cable per the Blue Sea calculator (4/0 at 10-feet is rated at 445amps max) - Circuit Wizard - Blue Sea Systems
https://baymarinesupply.com//bosns_corner_wire_sizes

I try to follow the 3% loss rule to maintain a generous margin of safety.
If a winch is used to its full potential, make sure that the wiring will maintain integrity.

Here's a link to the Blue Sea power switch mentioned above - https://www.bluesea.com/products/300...Battery_Switch
and the Blue Sea power post - https://www.bluesea.com/products/cat...tors/PowerPost
I used a power post to replace the jump start post.
If you want to use a high power post to replace the jump start post, check here - https://www.bluesea.com/products/210...3_8in-16_Studs
or
https://www.marinco.com/en/search?keyword=bus