@tmkhan:
In my opinion, its original engine 18R is good enough to carry you and ur family around town. If these engines are in good conditions, they will run for years.
Alterations is a costly exercise, and mostly it is for increasing performance of car. you will be needing to upgrade brakes, change transmission etc. And the dilemma is, if it gets wrong then you will end up in nothing.
Rather then spending on changing engine, do the following in one go:
- Rebuild engine with original spares (only if it needs overhaul)
- Get a body work done i.e Dent/Paint etc (if needed)
- Get a complete brake service (Compulsory)
- Get a complete suspension overhaul (Complusory, i would suggest replace suspension part instead of repairing)
- Get electrics alright
- Install a A/C
- Get the seats and interior accessories upto date.
- Replace all tyres
18R is good engine, and if tuned properly can give you good mileage as well. Getting a good CNG tuneup will add economy.
Let it remains a nostalgic japanese car, dont mess with it.