I have been reloading the 7.62x54r for a number of years. The length of the bullet is as far as I am concerned a non-issue. Just long enough to be seated in the case for enough tension to adequately hold the bullet and fit the magazine. Think of the 30-06. It has many different bullet lengths and weights. All will work. If you are going for bench rest accuracy, the bullet length will make a difference because you want to load it to very close to the lands.
For my Mosin Nagants, I use either a .311 or .312 depending on which rifle that is going to shoot it. For all but two, I have had great results with the Rem 180 gr rn in .311. It has a longer bearing surface than most of the others and for me more accurate.
As for as what else is needed but the dies, the proper shell holder. I don't have anything else. Now if you want to try .308 bullets, you will need a different expander ball for the sizing die. For me, .308 bullets have given me very poor results.
Now for length of the actual bullets here are a few.
Hungarian HB 1.313 in. 183gr .311
Hungarian LB 1.121 in. 148gr .3115
Albanian 1.281 in. 151gr .311
Hornady 1.068 in. 150gr spire point .312
Hornady 1.11 in. 174gr RN .312
Remington 1.062in. 180gr RN .311