Using SparkIV, scroll down to pc;models;cdimages. Open vehicles.img. Go to selected vehilce you used to replace with the 
Hydramax. Select the ".wtd" file of the vehicle and then click "Edit" up top. Select the skin image and then click "Import" 
up top. Open the downloaded image. You may do this for each texture (4 of them) along with the optional emergency light colors. 
Once all that you want are changed click "Save and Close". BEFORE CLOSING SPARkIV, CLICk "REBUILD" AND "SAVE"! 
Make sure your vehicle's line in the vehicles.ide has "+livery" added if not already. Start your game and enjoy! :)

If anyone would like to get me this, I will do any and all requests of anyone on the site as a debt of gratitude to the public 
for their gift!

http://www.turbosquid.com/3d-models/3d-model-ladder-truck/700409

-2Square
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-==MODEL CREDITS==-

= CAMION HYDRAMAX AERV ELS OSL EDITION =-

- NAME: Camion Hydramax AERV ELS OSL Airport Edition
- VERSION: 1.0
- LIGHTBAR: Whelen Mini Edges
- MULTIPLE LIVERIES: Yes (4x)
- OPTIMIZED FOR: Firetruk
- MOD STATUS: Complete - 100%


- CREDITS:

Original model by Ubisoft Reflections, ripped by stratumX, converted and mapped by Dhruv.
Whelen Edge by KevinDV, modified to Whelen Mini Edge by corleone.
Whelen LED modules by Ridgerunner Designs, textures by Bxbugs123.
Handling by Jayone87 and Dhruv.
Liveries by SwedishModding.


- NOTES:

Use ELS secondary setting "H-3" to turn on the work lights.
Rembember to add "+livery" @ vehicles.ide.


- PARAMETERS:

Handling.dat

FIRETRUK 11000.0 4.0 80 0.0 0.0 -0.4 0.0 7 0.10 0.3 105.0 0.2 0.50 0.15 40.0 0.90 0.75 15.0 0.15 0.45 1.4 1.0 1.0 0.20 -0.18 0.0 0.60 1.0 1.0 0.8 1.5 0.0 40000 8 300000 2


Vehicles.ide

firetruk, firetruk, car, FIRETRUK, FIRETRUK, VEH@VAN, VEH@VAN_RI2_LE2, 100, 999, 0.3407, 0.3407, 0.3, 2, 1.5 ,1, noboot+avoidturns+big+truckfirefx+truckenginefx+livery