Hey,
A few years ago I set out to have an example of each German K-98k sniper variant built. It has been a process but I am down to the last few. So you may want to start by picking which variant you would like to build. The Turret Mounts are the most iconic in my opinion, however finding people that do them correctly can be a challenge sometimes. The different variants are Short Side Rail Type 2, Short Side Rail Type 3, Low Turret, High Turret, Single Claw, Double Claw, Objective Mount, Sweptback, zf-41, Long Side Rail (band or split ring). Then there are the field armorer builds that were built with captured Soviet Scopes.
Also what do you plan on doing with the rifle? Vintage sniper matches, conversation piece, hunting rifle, or occasional range gun? How accurate of a clone do you want it to be?
And for the glass........the reproduction glass is junk. Your best bet is to find a period or pre war commercial optic. They are built much better, are repairable, and usually fit the condition of the rifle used in the build.
If you have any questions at all please let me know and I will help as much as I can.
-Brian