Hi Ganesh
If you purchased the cab kit for the 49 it only comes with 4 rear mount shakle bushings. You will need 4 bushings to rebuild one mount. As you know you have 2ea
The kit for the 49-54 comes with 8 bushings.
Here is a pic off my truck
1950 rear cab mount Sorry the pic is out of blurry
When I rebuilt my cab mount shackles I found the original rubber to be in good shape. So I just reused the originals.