To make a weapon use the 8x scope, you need to change scope_name to
scope_name = val_quest_scope_x8
But then you can't use any other scope but that with it.
To make the Trophy AK upgradeable, you need to edit the following. Find the quest_items.ltx (misc folder) and look for:
[esc_quest_akm47]:wpn_ak74 $spawn = "quest_items\esc_quest_akm_47" ; name and section in level editor description = st_esc_quest_akm47_descr inv_name = st_esc_quest_akm47 ; name in inventory inv_name_short = st_esc_quest_akm47
ammo_class = ammo_7.62x54_7h1, ammo_pkm_100
upgrades = installed_upgrades = upgrade_scheme = fire_dispersion_base = 0.5 hit_power = 0.8, 0.8, 0.8, 0.8 can_trade = false (You can add "scope_name = val_quest_scope_x8" to make it use the 8x scope.)
Here, delete the lines
upgrades = installed_upgrades = upgrade_scheme =
Then the standard upgrade path for AK is used. But taking the flatness upgrades will override the damage values, almost halfing damage.
I forgot to add: To upgrade the Trophy AK, you also need to add it to the weapon list of a technician (in stalker_upgrade_info.ltx). You need to add "esc_quest_akm47" to the weapon list.