Please be careful with your terminology, Zirk fittings are short, pipe threads(SAE and metric, be careful) on one end and grease nipple on the other end; thread into a shackle bolt and provide lube. A shackle bolt is lubed via a Zirk fitting.

Looks like you need shackle bolts and shackles and appropriate Zirk fittings for your truck.

Ed


'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.