All discussion about lathes including but not limited to: South Bend, Hardinge, Logan, Monarch, Clausing and other HSM lathes, including imports
Having to buy and use an ER 40 collet system on that length of material that still won't fit through the spindle would just be a way of providing the rotary drive to the part. The fastest, most repeatable and accurate method of doing that job would be to just center drill each end and turn the part between centers. Flip the part end for end and do all the machining at the tail stock end for each one. I already have a full set of the 40's and still wouldn't use them for a job like that. Mount some 1" or larger diameter scrap in your 3 jaw, tighten well so you know it won't move then turn a 60 degree point on that. It's now as concentric to the head stocks C/L as your lathes head stock bearings will allow. DO NOT remove that center from the chuck until all the parts are completed. Use one of the chuck jaws to drive the tail on the drive dog.