Also, now that I know the wonderful playground you have for a lunch room, I'll know where to go for my landing gear! -
My personal opinion is that fiberglass/carbon fiber would be the faster and less expensive way to go. If you're going to build a one-off, you won't even need a plug and molds. The cost could be spread out over a number of years, the more expensive items being the powerplant, landing gear and instruments. If you've got access to a machine shop, the landing gear is no longer an expensive part of the build.
The Bentley drawings will give you a good start, but you're still going to need a lot more P-51 technical information including as many factory drawings as you are able to source. The outline or shape of the aircraft is only a beginning. There is a myriad of details, and I'm afraid that the more you research the P-51 and the more knowledgeable and familiar you become with the aircraft, the more you'll realize how little you actually know.
One advantage you have is that factory drawings are available. I've had to develop my own working drawings from maintenance manuals, photographs, and measurements I've taken myself. It's a lot like playing Columbo. (remember him?)