The Stovebolt Site Forums The Shop Area Driveline rear springs '49 3600

http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0462.htm
That's what the manual shows, but I took the advice I found in a previous thread and drove the pins out from the back (there are holes in the frame so that you can place a drift or punch on the backside of the pin and hit it with a hefty hammer). Just make sure you remove the lock bolt first; otherwise, that pin won't go anywhere.
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0460.htm
Figure 86 at the top of the page shows the type of shackles you have.