Hi and welcome! I just looked at the brochure for 2004 Towlites, and it doesn't say, but I'm reasonably sure it's the same as mine - A 3500# torsion bar axle made by Dexter. I don't think the axle has anything to do with the brakes, you just need the drum size, which, as I recall is 10".
My trailer is a 2007 17 Ft Towlite.
Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH
2014 F150 Platinum 4x4 3.5L EcoBoost SCrew