4 speed ka-booom !

Good advice on the auto but the 4 speed appeal is understood.... With the hard coupling of the drivetrain on a 4 speed in a racing discipline that emphasizes maximum traction, the impact loads are always going to be rough. Some gear oils like RedLine advertise better shock proofing, but I can't say if that works or not. (I've used it in rallying but that is more for endurance, not shock proofing.)

Now on dirt or gravel, it would be a whole different story: auto's are undesirable (IMO) and 4 speeds are the thing...