What you have described is exactly the kind of project I think concrete5 excels in, being able to create structured pages like this.

The main way I would approach this is via custom page types, custom page attributes and the use of the composer.

I'd create custom page types for the vehicles and categories, with attributes for the image thumbnails and the other pieces of information you need to display a vehicle.

Although there are ways to point a page at a file set to create a gallery (something I'm actually going to blog about soon), in this case I'd probably cheat a little and just create a series of image attributes to store the vehical images, something like main_image, image_1, image_2..., image_8. If I needed more than 8 images down the track I'd just add a few more attributes.

Featuring a vehicle could be done by creating and using the special is_featured checkbox attribute, that can be used by the page list block.
http://www.concrete5.org/community/forums/usage/how-to-add-the-andq...

Vehicles could be categorised by simply creating their pages under category pages, using page aliases for multiple categories if required.

The trickier bit of data entry is the table of specifications - you could try a text attribute with an editer for this, but I'd suggest you keep this relatively simple.

I'd set both these page types up in the Composer, making it so you could only place vehicles under category pages.

To list vehicles, you would use the page list block a lot, creating custom templates to output the data you needed.

For the gallery page, you would use the page list block with a custom template to pull in the vehicle images and links, and further down the page add a gallery of your choice for your add-hoc images. You'd set up your category page to have by default a page list block that pull in pages underneath it.

I don't think you'll need to develop any custom blocks as such, just customise the output of your custom page types and custom templates for your page list. The coding you'd need to do would be fairly minimal and the things you'd need to know are well documented (and discussed in these forums).

If you've not done any of the above yet, and it all sounds like nonsense, have a look at a video I put together the other week for this, it pretty much covers all of the above -http://www.mesuva.com.au/blog/technical-notes/setting-up-and-custom...
(not trying to self promote here, it's just that I put code snippets underneath the video that are handy too)

I've built this kind of structure many times in concrete5, http://www.bdms.com.au is a good example of this (just pretend the machines in this site are your vehicles), or http://www.uapcooling.com.au, which is a good example of using categories with thumbnail images, linking to products with specificiations.

Concrete5 is just such a great system for this kind of problem, you end up with something that clients can actually manage themselves!

Mesuva, thanks so much for your reply, and for going into so much detail. I'll be giving all of this a go shortly, and will let you know how I get on.

Not related to your application, general tip:
http://www.concrete5.org/documentation/how-tos/developers/organise-...