I also work on cars. Mostly I just fix the bare minimum. I don't spend a bunch of money to modify something up into a custom car or anything. But I do like to replace the stock parts with better ones when they break. Or if I decide that a small modification is worth the money.
I'm currently in the process of taking apart a Gen I Chevy 350 (5.7 Liter V8 engine) because I want to see how the engine looks with 200,000 miles on it. I still haven't decided if I want to rebuild the engine and keep it in it's current home, or try to find a cheap rolling chassis to put the engine (and transmission) into. Either way, I should end up with a rather cheap car that's better than anything car companies make now. So I may end up restoring a 1993 Buick Road Master Estate Wagon. Which is a weird car to restore, but the point is for a cheap, reliable, practical, daily driver. You can't really beat an 8 passenger car that can easily fit sheets of plywood in the back, has 300 ft/lbs of torque, and gets 18mpg on average, but about 23 highway. The gas mileage isn't the best, but it's a fun car to drive, doesn't look fast so you don't have people trying to race you, and the car is so cheap that it ends up costing about the same as a brand new car that gets twice the mileage in the long run. (That's price of car + insurance + gas.) Besides, a big car with lots of power is better than a cheap KIA or a little Ford Fiesta.