Rear end swap

You will need to find out the gear ratio of your current rear end. There should be a tag with information on one of the differential cover bolts. The gear ratio is important as it must match the front axle, otherwise you will not be able to use the 4 wheel drive.

Thanks, but now I have found a rear end the same as mine in a 97 model 4x4 with same gear ratio would it work?

It should be compatible. The Ram 1500 was the basically the same from 1994 - 2001. This site has info on your RAM pickup. (https://www.allpar.com/model/ram/1994-ram.html). That being said, you should make some measurements (spring mount plates, overall width, etc) to make sure but it should fit.