The followers were made for a specific caliber.The illustrated ones have a ring on them so they would only go so far in a casing.The wad was inserted first to the depth of the ring.Bullet seating and length was accomplished by a "ball seater" in which the ball was inserted into the seater,then the loaded casing was inserted into it and forced in until it bottomed the rim out on the tool.The ball seater was caliber and length specific as far as the case used.In your case it would have been marked .45 2.1 inch indicating the case used but not the bullet.
All the illustrated tools for loading are marked as to case lenght of the cartridge regardless of bullet weight.The standard Sharps loading for their 2.1 case was based on a 420 grain paper patched bullet and 70 grains of powder or the same powder loading and a 400 grain grease groove bullet.All the tools illustrated and IDed are marked as to caliber and case length and would be for that specific Sharps loading with 70 grains of powder.
A set of tools for a Sharps of the Period consisted of-
Mold
Bullet Swedge for sizing bullets
Wad Cutter
Cap Awl for depriming
Lubricator Mold for making grease cookies
Follower for seating wads and grease cookies
Powder Charger A dip measure is illustrated.Charge specific,for that casing 70 grains.
Brass lLoading Tube A drop tube.
Shell Crimper The ball seater
Shell Reducing Die and Punch For resizing fired cases.
Re-De Capper
Base and Nose Trimmer for bullets.
All for $6.00 FOB Hartford,Conn.
Later Edit: After re-reading your OP some thoughts.For what you are trying to make you would about have to back engineer the tools based on your load given the difference in powders and case capacity vis a vis old/modern when looking at the old catalog information.The old balloon head cases in use back then had a greater case capacity than modern brass.It can run 5 to as much as 10 grains difference in some cases.The grain size of powder back then is very different than what's on the market now.You need to figure out the load with a wad compressed the way you want it,then measure a height to top of case from the wad,make your follower to that measurement with a stop on it at that height so it goes in the case no farther.That would duplicate an old one.For general use leave off the stop,but the old Sharps tools were all pretty much set up for a specific caliber/case/bullet/powder combination.