I really dont' think that the level system is realistic at all, but even applying it I personally have a hard time imagining any real world person as more than 5th level or so.
There might be a handful of people out there whose training, education, and experience was sufficiently broad or deep to qualify as sixth or seventh level but these would be the most capable people on the planet.
As for Audie Murphy, I think you are looking at a convergence of talent with luck. Afterall, in a war with ten's of millions soldiers, someone is bound to perform well above the statistical mean. I'm not taking anything away from Babyface Murphy, because he was clearly a brave and capable man, but by far and away clearly the most important aspect of his surivival was analogous to his ability to string together lots of 20's at a time when his foe was not rolling well. It doesn't mean that he was more than 5th or 6th level.
A better system for resolving a real person into game attributes is figure out how much time you have spent training in various fields, then use those numbers as guidelines to convert to GURPS skill points. Add on appropriate ads and disads, add or subtract a point or two for every standard deviation you are from the norm in intelligence, agility and what not, and you have a character sheet.
Last I added up the totals, I was a 60+ GURPS character, and my knowledge and skills are not generally regarded as insignificant. I'm going to be very suspicious of anyone claiming to be a 200 point GURPS character who has time to spend on these boards.