I'm in the process of making several upgrades to my $24 Fullerton ST4 HSS, a.k.a. the "Fat Fully". Changes include the following:

Pickups - The stock p'ups were remarkably good for such a cheap guitar, but they're a bit on the harsh side and lacking warmth. I picked up a set of black-cover overwound Strat p'ups from Guitarfetish.com on a "blowout sale" that I read about here--the whole set for $17! The description sounds like they're intended to be "Texas Special" clones. I have Fender CS Texas Specials in my Strat Plus and love 'em, so we'll see how close in tone these are. For the humbucker, I had the one that came out of my Epi Dot when I bought it, which the seller said was a Gibson '57. I'm not sure if that's true, but it was a very nice sounding 'bucker that I only replaced because it was a single-conductor braided-shield type and I wanted to do some fancy wiring on the Dot that required a 4-conductor model (see THIS THREAD). I physically swapped all the p'ups last night but didn't have time to solder the new ones in yet. Will get that done tonight or Saturday.

Nut - The Fat Fully came with the kind of cheap plastic nut common to many budget guitars. I got a pre-slotted Fender-style Tusq nut from StewMac (#4750, $6.29), but it's got a raised "key" in the middle of the bottom surface that will need to be sanded or ground off, since the nut slot in the guitar doesn't have a corresponding cutout to accommodate this key piece. Also, the Tusq nut is a bit wider than the stock nut & slot, so I'll grind that down a bit to fit the slot.

String Trees - I've noticed that the stock metal string trees on the Fully tend to squeak on hard string bends down low on the neck. I ordered GraphTech string trees ($5.13) to replace them, which should eliminate this minor nuisance. However, the GraphTech trees are both of the "tall" type, and the Fully uses one tall tree and one short one, so I'll have to grind one of the GraphTechs down to the shorter height.

I'll make a follow-up post after I complete these changes to describe the impact of these changes on the tone and playability of the guitar. Hopefully, these will be positive impacts, since I'm sinking an additional $28 into the guitar, ballooning it's cost to over $52!!