55.2-59 55 spring shackle replacement/upgrade

[BOXER957]

I have a 55 2nd series and all the parts to convert to 4x4. I'd like to know if the newer 58ish spring shackles will fit...I'm a bit leary on the older style held together with a carriage bolt and would like the newer style with nuts on the end of the pins....obviously more concerned with safety than originality...if I can't change the style, anybody running the carriage bolt style ever have issues with the shackle coming apart on hard cornering?

[burnin oil]

When I converted my 57 over I just used the factory springs. 57 GMC dually. I added a block to the rear to level it. The only real issue was hooking up the manual steering.

[_Ogre]

all the replacement shackles bolt together. yeah, i looked at the 1/4" bolt and wondered how long before it broke. this is new shackles on the back of my 58

[BOXER957]

55 is supposedly different...a one year only type thing...I also used the bolt togethers on a 58 I did but every place I look the 55 is the one with the carriage bolt...my question is ..are the frame mounts and springs the same width? the hole in the spring the same size? anybody been told they had to do carriage bolt, gone with the updated one with success?