My '85 Ram was purchased without a spare tire.

I can find a wheel & tire locally, no problem......but how does it mount to the under bed/frame?

There's usually a bracket that holds it but Most remove it all together. Some trucks in the 70s had a factory in bed mount. I made my own in bed. I'll post pics tomorrow of it.

I can find a used 15 inch rim/tire locally, no prob there.

Anyone have whatever bracket/mount I need for the spare tire?

2 hooks. One is fixed, the other threaded. Along with a bar to cradle the spare tire.

I use a spare tire winch from a 94up
You have to bolt or weld a piece of angle between the frame rails with a piece of 2X4 bolted in the middle & 4 holes to bolt it in

I did this on a drag truck I had to move the ballast bar up & down to add or subtract weight

Pretty sure Dodgeconnection sells what you need. I remember this being brought up before

Yep they have them. your looking at just over $100 without shipping.