You can always try and it may require some specific settings on the mesh portal (turning off the higher MCS rates, only using legacy rates, etc). But a vehicle mounted mesh solution is not supported in AOS and so if the portal/point stability is an issue, there won't be much of a fix from Aruba on it.
Using the 501, you can always put the 501 as a mobile device and then a low cost Ap in the cab wired to the 501, that has been done with pretty good success.