as you said, after patch 1.27 you can drive it but they improve the garage memory system, so if you stock any rare vehicle expect a ban because its not possible by a legal way, they deleted the roosevelt too, and the snow cars from every garage with the 1.27 update.
in 1.24/1.26 you can have it in your garage, but you can't drive it, because it wasn't a legal vehicle online, and the way they prevent modders to use it online was that if you get the DoD online it will explode as soon as you get in the car.
Try and download the unlock DLC and special vehicles and weapons mod, you will have the blimp, the special weapons as the fireworks launcher in ammunation but I'm not so sure about the rare vehicles in the garage so check it out at your own risk, it's a giveaway to have those cars in your garage and so watch out for the ban, besides downloading that unlocker, will be memory editing too so mod at your own risk.
My recommendation is to just spawn it, customise it and save it on the mod menu settings, and then spawn it every time you want to use it.
If you don't have a mod menu, or the menu you are using doesn't have that kind of option, check out another menus.