It's exactly 250 miles from the Las Vegas strip to my house, and I live directly in your path to Enrique's shop, which is another 50 miles.
So 300 miles from Vegas, and the speed limit on interstate 15 from Vegas is 75 mph, but everyone drives 85-90, so you should be able to make it 3.5 hours.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".