The problem is how light any small truck is in the rear end. If you've ever driven an older Hilux you'll notice they behave themselves when they've got a load in them. When they're at kerb weight they are jittery as all get out (they are horrid to drive - Mitsubishis run rings around them...) Install a medium load rear stabiliser bar, decent shocks and some wider low profile rubber and it will go a long way but they were never meant to lap a Lotus or an R8. Double wishbone front end can be tweaked and re-engineered but its all go to do with either the bucks or your own skill. I got my own ideas on improving the MM/D50 on top of suspension upgrades. I think the drivetrains' centre of gravity can be lowered. The engines and gearboxes sit pretty high up in the frames - only road block to dropping it down is the drag linkage in the steering but like all things there's a solution somewhere around that.