Sounds like your not really taking care of it dude, hence why no one is really replying.
I painted my wheels in a plain silver from supercheap auto. I used 240, then 600 grit sand paper to rough up the wheels, then lightly with 800 to get it all smooth. Then applied 3 coats of paint, lightly ;). Clear coat them will be alot better!
As for engines, K series motors are slow, leak and in efficient. however they are Reliable and will last forever if you treat them with respect. You will get beaten by stock v6 commodores and the humble prius. Thats the ugly truth.
Put a 4k in, with a good tune up (spark plugs, fuel filter, air filter, points, condenser and get the timing right)
My 4k made 32kws at the wheels (40hp) which was 10% of my last weekend car that i sold. And to be honest. Its almost just as fun!
Enjoy the car the way they were made :)