In this article gonna give you guys an overview of the things you can do to your Marshall Senator(can be purchased here: https://marketplace.secondlife.com/p/MARSHALL-Senator-Police-Cruiser/24605369).
It's mostly gonna be a copy paste from the manuals for other new-ish GEMC-scripted vehicles, but whatever.
1. GTFO! support - this vehicle supports GTFO! system(https://sl-gtfo.com)
 out of the box. You can attach your prims 
to the vehicle and use them as a visual cargo. To do so, change the description of your 
cargo prims to "CARGO"(without quotation marks) - that will make a prim be recognized by our visual cargo system made for GTFO! Additionally you can use moving prims prefixes with the "CARGO" description, see below.
 2. Now, did you know that you can make 
your addon prims move with the vehicle's doors?. In order to
 do so, add "ADDON_"+[moving prim's description] prefix to their descriptions.
So, if you want your prims to move with the driver's door, set their descriptions to "ADDON_DOOR_FL",
"ADDON_DOOR_FR" for the front passenger's door, 
"ADDON_DOOR_RL" for the rear left passenger's door,
"ADDON_DOOR_RR", for the rear right passenger's door,
and "ADDON_BONNET" for the bonnet.
You can combine these prefixes with other stuff in the prim's description, in example: "ADDON_TRUNK_CARGO" - that will make a prim move 
with the Senator's trunk and be recognized by GTFO! system(very useful 
if you want to have your cargo mounted on that fancy cargo rack in the 
back).
Or, for example, I want to have a little curtain on the passenger's door, so I can set it's desc to "ADDON_DOOR_RL_CURTAIN*0.521", so it can be identified by the addons script, and by the main curtain script, that may record some data in there(not that we need to resort to this kind of thing anymore, since we have the linkset data feature now). 
Anyway, keep the fact that you can make one prim participate in multiple systems, in your mind. Also, remember that the more addon prims there is, the slower things perform(now slower, but more choppy, whatever). So if you can combine your addons for a single door into one prim, make sure to do so.
3. Another thing that seem to be puzzling some minds is the wheels. Following text is a straight up copy paste from my other manuals: 
EasyWheels project - I've added some code that lets you 
install any crappy ripped wheels(provided they're 1 prim each), 
regardless of their rotation, and without having to fiddle with numbers 
and whatnot. It can be done in a few simple steps:1 - Set your car straight.
2 - Enable "Edit mode" via vehicle menu.
3 - Unlink current wheels and link yours.
4 - Set correct descriptions on your wheels(WHEEL_FL, WHEEL_FR, WHEEL_RL, WHEEL_RR).
5 - Turn off "Edit mode". It's done.
Edit
 mode and all the car rotation steps can be skipped if you're sure you 
can set wheels straight on your own. Failing to do so will make your 
wheels wobble when in motion.
4. GMLS support: Yes.
The GMLS ID is LR_MARSHALLSEDAN_BASE
5. The vid - I've recorded a tiny video on the addon prims in case the text above is hard to understand. Sorry. Watch this: https://www.youtube.com/watch?v=VRapvNI8oCs
That's about it. I could write a little bit about scripting your own addons, but whoever's doing it, they already know how to. Track vehicle's linked messages, hook stuff up, you get the idea. Aight cool.
GEMC, 2023.
