we ran a 4x4 for a group of bikes to chernobyl via belarus in 2007. the organiser wasn't sure wether to have us along, he was glad he did when the alternator went on his bike. also on the rougher sections we were able to carry the bikes luggage (most were sport bikes) and when one of the bikers was ill he could ride in the truck while his bike went on a trailer.
the upshot was we've been invited back this year!
I would go for the pickup because you can get a bike in the back if you need to (a trailer isn't viable in morrocco I would say).
carrying the bikers gear would allow them just to concentrate on and enjoy the biking.
the only rule we have is that all the luggage must be able to be carried on the bikes in case the truck has a problem, oh, and if your on the truck you contribute to the fuel!
NIssan navaras are prone tp blowing their engine bearings when running hot (not that hot, just motorway speeds) although mods are available. the ford ranger is a good inexpensive truck but check the synchro on any with over 50000 miles and make sure it starts from hot as there are problems with the fuel injection system on mileages over 80000. both are expensive to fix. I used an L200 for chernobyl but I don't think it is suitable for Africa, not tough enough. my choice would be a 2.5L hilux. there is a price premium thanks to top gear and finding a good one is hard as they are a victim of their own reputation but they can be found. don't necessarilly turn down an old one, go for condition. in fact an old one may be handy as parts can be easilly obtained anywhere, there are loads of them in morocco.
you DO NOT need a fully expedition equiped truck for this, you are not going half way round the world. Just make sure the basics are in good nick, drive train, suspension, and cooling. Fit a new clutch and waterpump and take the old ones with you, then you know they will fit. same with any parts you replace. take a 2 barrel footpump as a backup to any tyre compressors. waffle boards are cheaper and more versatile than sand ladders. take a long handled shovel and a tyre pressure guage. the truck can carry a range of tools etc for the bikes and itself. stick with steel wheels and go for 7.50x16 tyres for ease of availability and extra ground clearance.take two spares, the rocks in morrocco are bad news for tyres.
I drove to the gambia with 2 heavilly laden but totally standard H60 landcruisers on this basis in 2006, having previously done it in a stock suzuki sj413. My budget for the two landcruisers together, including all the preparation (no tat, just replacement of suspect parts and servicing) was less than your total budget.
you
do not need to spend a fortune on 'essential gear' to go to morocco and beyond!
there is a tips and advice section on budget expeditioning in my book
Me, dad, and the Plymouth to Dakar suzuki expedition on eBay (end time 31-Jan-11 18:54:21 GMT)