Re: all but the chain
Don't worry about tuning or mods until it's broken in fully. These engines usually take 300-400 miles to settle down and run up to full potential.
Once it's stable and fully seated, you can start looking for more.
I'd suggest a smaller rear gear and a pipe for better cruising speed.
If more is better, then too much is just enough.
If you can't afford it, build it yourself.