Brakes or Cylinder heads?

So after having driven my '68 Barracuda for the summer, I now have it ready to go back into the garage for winter - and money for upgrades. Now, I'm not exactly rolling in money, I'm a high school student (with no job because of school) with a garage, some tools, a hot rod, and about $800 to spend on said car. And I have a major dilemma on what to spend the money on.

Honestly, the engine runs fine. It's a 360 small block bored .30 over with a mild cam and some headers. It needs a little adjustment, but it's fine; I don't need to throw in a massive cam or dual-quads or aluminum cylinder heads on it. But that doesn't mean I don't want to. I've been considering putting 360 Magnum cylinder heads on it, which I figure I can afford, but there are other things I can do too. I have a second carburetor (Holley 600cfm 4 barrel, identical to the one currently on the motor), and I could purchase a 2x4 manifold for roughly $400. This would be more of a *****-n-giggles dealio rather than performance oriented; there's no way my engine can move 1200 cfm through itself.

Conversely, I could do suspension/handling upgrades. The car has 4 wheel drums, and I need to rebuild them (at least the fronts) this winter regardless. For about $600, I could convert it to front discs, and for a little more, I could replace all of the bushings/shocks/etc. because they are shot. Also, being able to go fast doesn't help very much if I can't stop.

Finally, I could spend my money on the actual car itself, as in the cosmetics. The car is far from spotless, both inside and out. The frame and floorpans are in pretty good shape, but the body (esp. passenger side) is pretty rough. With a little work, I could replace the carpeting and reupholster the seats, and maybe some of the other interior trim components. The only reason as to why I am hesitant to do this is because it has been suggested to wait on cosmetics and restoration until I can do everything all in one go - i.e., ten years from now when I have $15,000 to spend on the car. I'm not how relevant this is for interior work.

What do you guys think? What should I spend my money on?