The normal stuff applies:
- Ensure your ignition system is in good condition
- Fit a single Weber on an adaptor plate
- Fab up a better exhaust manifold and exhaust
- Find a hotter cam
- Rebuild with slightly larger pistons and higher compression
It still won't be great and you'll be battling sub-standard head/port design and a super-low standard compression ratio. A turbo is a nice idea, but if you can't fab a setup yourself then you're out of luck. Or maybe find the biggest blower you can and run it on methanol.
There's a reason few people do much with these motors.