In .308 w/168gr match ammo the NDM-86 is capable of phenomenal accuracy. In 7.62x54 there is no true lightweight (appx 150gr) match ammo available so you can't realize your Dragunovs true accuracy potential.
Your best results will probably be w/surplus 7N1 SVD ammo (if you can still find any) but it is corrosively primed so very careful cleaning is required after shooting to neutralize the primer salts.
Due to the lack of true match ammo, using a really expensive scope is overkill.
The 4x PSO-1 is fun to play with from a historical perspective but limits your distance capabilities. I'd suggest either the 1P21 or one of SWFA's Super Snipers: http://swfa.com/SWFA-SS-Scopes-C1719.aspx
HTH, keep us posted!...
Tomac