Baja vehicles or rally-cross cars have long been a part of automotive culture, many people like to race through forests and jungles in 4WD monsters that run on racing alcohol, others like running through desert sands or beach dune cruising. All of these are contributors to off-road race culture, and there are a few notorious platforms for people to build their race car off of.
Of course, I could list 5 vehicles that are not practical for this project, but would work well such as the Alfa Romeo 4c, Fiat 124 Spider, or maybe even the Porsche 718 Cayman. But I have sense in me, and I know the criteria used to evaluate these 5 superlatives should consider the accessibility, such as price and rarity.
1) Porsche 911
I may be biased to this platform, I admit it is my favorite chassis of all time probably. I know that these are not that easy to come by, but you could pick up an early model shell for under 7k and start from scratch! Already known for its durability, the 911 has one numerous racing awards... even off road. Safari 911s are a popular choice among many enthusiasts.
2) Subaru WRX
Yes, the famous rally car. It is no surprise that you could make a monster out of one of these, but what makes them truly special is the customizability of one of these subies. Parts are everywhere. Most of these have beautiful 4WD systems, and the proof is in the rally championships that this car holds prestigiously. It's pretty simple actually, just slap a bigger turbo on and some mud tires and you are good to go!
3) Volkswagen Beetle
Oh boy. Where do I begin. So many of these machines were manufactured over the course of 60 years, that the main advantage of these vehicles is their availability. You can literally get an old model for a few hundred bucks if you look hard enough. These bugs are so mechanically simple that you can pretty much do whatever you want to them. There is a lot of parts readily available to retrofit these, but its pretty much a blank canvas for creativity. We saw The Grand Tour do this across the coast of Africa in their custom-made buggies.
4) Honda CRX
The Honda CRX is a popular choice among street racers, but less common among off-roaders. The downside is the FWD layout of the drivetrain. However the rugged dependability of Honda and accessibility of parts would offer a pretty promising ride, with a little bit of work, A well balanced chassis and simplicity of the vehicle itself makes the CRX a good option for JDM lovers.
5) Datsun 240z
Another great platform to build a rally car on would be the famous Datsun 240z. Another simple machine just waiting to be an expression of creativity, reliable and plenty of space for a huge turbocharger. These coupes don't only look great, but they handle well too. I would love to sling one of these around in a circle on some dirt. With some heavy modifications, a Datsun would make an excellent rally car.
Did I miss any? Let me know in the comments what you would build.