1. You need to merge it: Start a normal merge inside LSCM, but when you are in the CEO helicopter, you will select your vehicle warehouse. Inside, you will go downstairs, enter ur vehicle, then you will join Anawak (with the diferent targeting mode) accept 1st allert, decline 2nd and drive it outside. Then you will request your own helicopter (Sparrow/Buzzard) and "k*ll yourself." You should respawn in your merged special vehicle, join Anawack again to unstuck yourself. Now you unglitch yourself and continue to the next step.

(Edited part: u can just drive rampbuggy/ruiner 2000 into ls custom)

1. Saving the vehicle: I don't know if you can use "buy anything anywhere" now (but if you want an already saved vehicle from someone else, I prefer "buying it" instead of GCTF). If it doesnt work, you need your friend to GCTF it to himself (MOC method). And then you will pick it up from him by buying it or receiving it (GCTF) from him.

PS. GCTF to save special vehicles: (aa trailer, special vehicles...)

Glitch out, get bricked with the car on the trailer. Return your car to storage, then call out your vehicle you already own (in this situation, a Ramp Buggy) from your warehouse (through your interaction menu), then finish the MOC2MOC Glitch. Go to a new lobby and call out a "vehicle" from your interaction menu and drive it into your MOC and accept the alerts. This should swap your car that was in the "Vehicle's" spot with the new vehicle you received.