One of the most common axles found on trailers around 7,000 lbs and smaller is the Dexter 3500 lb axle. On smaller ones, they use 1 axle and on bigger ones they use 2. 2 axles give a better ride IMO and have several advantages including the fact you can drive on 3 tires for a while (don't ask me how I know this).
If you can get a trailer with a slide out to fit your weight limits and budget, I would certainly recommend it. You'll appreciate the extra space. The 4.7 V8 is a great, bulletproof motor btw, had that in my old 2000 Tundra and towed the old trailer in my sig for about 3 years.