actually, the pin through the strap loop inside the receiver is a recomended way. However, since that puts the pressure on the middle of the pin, not how the pin was designed, it just does nto seem like a good idea to me.
You go with the Warn receiver mount, but a cheaper way is to buy a solid aluminum ball mount, without the ball. Then purchase a drop forged twist pin style (not cotter pin style) D-ring shackle. Most D-rings are rated for 50K lb working pressure. The pin should be 3/4 inch.
Important, when using this set-up mount it so the shackle goes through the ball mount, and the pin on the shackle is holding the strap. In the event of failure it lessons the loose metal flying around.
More important, are you sure you bought a true recoverny strap? TSC and others typically sell tow straps. There is a huge difference. A recovery strap is made to stretch. It has material in it that will degrade over time. You should see blue fiber in the strap. If it ever breaks, throw the strap out imediately. Federal law requires the blue test material in a true recovery strap.
A tow strap is designed to not stretch. It is a static line.