One think though it has a brake drum on it and wheel cyliner. There is
a cut hydraulic line on the back.

Typical of repurposed truck or automotive axles reused for a homemade
trailer. If you get new bearings, make sure to get new seals, too.

I found an axle at TSC for 159 bucks that would fit it. But mine is
set up as a drop axle and the TSC is straight which I am assuming
would cause my coupler height to be wrong.

You could just get a different ball mount for the truck; probably the
cheapest, most varied, and most common towing part ever, other than
the ball itself--this assumes you are using a real hitch and not just
a ball on the step bumper. Got a welder? Reconfigure your trailer
hitch to change the height.

Or just grit your teeth and pay the shipping to buy a proper drop axle
from one of the mailorder places like etrailer.com, trailerpart.com,
northerntool.com (unless you happen to live close to one of their
retail stores), southwestwheel.com, or championtrailers.com

You'd then be able to rest secure in the knowledge that replacement
parts from then on out will be readily available and you'd know what
they are (the champion trailers site has a particularly useful amount
of information).

There's another option which acts like a drop axle when properly
configured, and has the added benefit of having a suspension: the
torsion axle. I'll let you consult google for the details. They
would allow you to either completely eliminate your leaf springs, or
if your trailer was made like some I've seen where the axle was
directly welded to the frame, add springs.

Note too that both straight and drop axles can be configured two ways,
over or under the springs, depending on which way the spring mount
pads are welded on, which gives you more ride height options. Simply
flipping them over isn't a good idea, since most trailer axles curve
up slightly in the center to make them tow better.

Also consider getting a hitch scale.
http://www.sherline.com/lmbook.htm has one listed for sale down at the
bottom, but read the whole article anyway.