The 6L wouldn't be a bad choice, it would be roughly comparable to a 12t brushed with TONS of torque. Top speed should be about 40mph (about a Revo's speed). Your runtime depends upon the capacity of the battery that you will use.
SH Z-Car, Custom Crawler, 8s Savage, 12s XTM XLB 1/7 buggy, 4wd 4-link rear/IFS Pro4 truck, Custom Hyper 10 Short Course, Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz