Interiors
Credits to CodeWalker (dexyfex and contributors) and GTA V Script Decompiler (njames93) for providing the tools to get this information.
This section is not 100% reliable until I can test them ingame. All locations seem to work just fine, keep in mind that you'll need to use entity sets to make them look proper.
Tuner Garage
Position: new mp.Vector3(-1350.0, 160.0, -100.0);
Entity Sets/Interior Props:
entity_set_bedroom
entity_set_bedroom_empty
entity_set_bombs
entity_set_box_clutter
entity_set_cabinets
entity_set_car_lift_cutscene
entity_set_car_lift_default
entity_set_car_lift_purchase
entity_set_chalkboard
entity_set_container
entity_set_cut_seats
entity_set_def_table
entity_set_drive
entity_set_ecu
entity_set_IAA
entity_set_jammers
entity_set_laptop
entity_set_lightbox
entity_set_methLab
entity_set_plate
entity_set_scope
entity_set_style_1
entity_set_style_2
entity_set_style_3
entity_set_style_4
entity_set_style_5
entity_set_style_6
entity_set_style_7
entity_set_style_8
entity_set_style_9
entity_set_table
entity_set_thermal
entity_set_tints
entity_set_train
entity_set_virus
Car Meet
Positions:
new mp.Vector3(-2000.0, 1113.211, -25.36243);
new mp.Vector3(-2000.0, 1113.211, 27.66735);
Entity Sets/Interior Props:
entity_set_meet_crew
entity_set_meet_lights
entity_set_meet_lights_cheap
entity_set_player
entity_set_test_crew
entity_set_test_lights
entity_set_test_lights_cheap
entity_set_time_trial
Meth Labs
Positions:
new mp.Vector3(981.9999, -143.0, -50.0);
new mp.Vector3(1210.0, 1857.0, -50.0);
new mp.Vector3(1569.0, -2130.0, -50.0);
new mp.Vector3(839.0, 2176.0, -50.0);
Entity Sets/Interior Props:
tintable_walls
Miscellaneous IPLs
tr_tuner_meetup
tr_tuner_race_line
tr_tuner_shop_burton
tr_tuner_shop_mesa
tr_tuner_shop_mission
tr_tuner_shop_rancho
tr_tuner_shop_strawberry