Step 310E (SE) qol changes

Hello, I would like to suggest two changes to the truck(s) Step 310E (and SE).

1- The suspension was fixed, thanks Saber/Focus!!

2- Add the possibility to use both Rear addons "Rear-Mounted Rack" and "Spare Wheel Mount" at the same time with the Sideboard and Flatbed frame modules.

I did a little modifications in the XML and both addons with those modules fits very well on the truck, very fun to use.