what axel is in my 1982 f250 ? 603946-4
The door tag is gone. I bought the truck for the flatbed. Got the vin tag and axel tag 603946-4. i really would like to use the rear end cause its a posi and i need 4:11. Hope it is. mike

 

Appears to be 3.00:1

Dana Holding Corporation - The Expert Axle Bill of Material

 

... and from the same link it appears to be a semi-floating Dana 61. I'd never heard of a Dana 61 before but Wikipedia says it's a version of the Dana 60 with different pinion offset so they could install taller gears (like your 3.00:1) Not clear if 4.10s could be swapped into it, but it does say that low geared Dana 61s are uncommon

 

Some rearends that are setup for a low number ratio like that, can be converted to a higher numbered ratio with a kit, that has the smaller pinion and a thick spacer that goes behind the new ring gear to move it over to meet the new smaller pinion. Not sure if they make such a setup for a dana 61.

As a side note, if you want this rearend for heavy duty use I would not start with a semi-float axle like this. You want a full float axle.