Leave your 16V 4age in there... If it's a 1989 then it
could already have a smallport 16V engine - the best of the 16v's. Although it is most likely a "redtop bigport".
All the specs and information you will need can be found in the reference section of
www.club4ag.com . This site has helped my through all of my developments and the info is good.
Don't bother changing or re-building the engine yet. The most important areas to start with are brakes, suspension and tyres.... and track time. Without track time and driver training your modifications will have little benefit.
Your "to do" list should be something like this:
Fit decent brake pads & straight rotors - pads such as Bendix Ultimate are good value for money for street cars.
Decent tyres - a set of decent road tyres on 15" wheels will be a good start.
Shocks - New shocks make a huge difference. See if you can find a KYB "sport" shock or a TRD insert, otherwise Excel G's are fine for starters.
Springs - A good set of springs will make a difference. TRD springs would be best
Bushes - Suspension Bushes make a big difference to how the car handles. Yours will probably be worn after a lot of KM's on the road. Try to get nolathane bushes or similar.
If you take the time to get the handling sorted and get experience behind the wheel it will pay off in the long term. Engine developments should be saved until you are comfortable with the car and the race track.