It is recommended to fully disassemble the SV-98 and insure it when attempting this quest. The empty receiver can be placed successfully in the spot, and you can sell the excess attachments in order to save some money.
Place the multitool in your secure container so it is not lost if you die during this quest.
Take these two items with you to Shoreline and navigate to the small rowboat on the beach by the gas station (pictured below). Once there, go up to the rowboat and hold down your interact key. This will start a countdown of 30 seconds. Once the 30 seconds are up, one of the two items will be removed from your inventory. Both items are not removed at the same time. Repeat this again to place the second item. Once you have placed the second item and extracted, the quest is complete.
The "secret spot" is found by the water next to the gas station on Shoreline. The related quest items need to be placed in the fishing boat.
Fishing Gear · Tigr Safari · Scrap Metal · Eagle Eye · Humanitarian Supplies · The Cult - Part 1 · The Cult - Part 2 · Spa Tour - Part 1 · Spa Tour - Part 2 · Spa Tour - Part 3 · Spa Tour - Part 4 · Spa Tour - Part 5 · Spa Tour - Part 6 · Spa Tour - Part 7 · Cargo X - Part 1 · Cargo X - Part 2 · Cargo X - Part 3 · Wet Job - Part 1 · Wet Job - Part 2 · Wet Job - Part 3 · Wet Job - Part 4 · Wet Job - Part 5 · Wet Job - Part 6 · The guide · Peacekeeping mission · Lend lease - Part 2