Non-hemi best performance for daily driver?

[Bladerunner]

What's the best parts to put on a 69727 non hemi 212cc with the rtc-9 head?

I ride a 2-speed auto motorized bike that currently tops out around 55mph. The engine currently has a 19mm slide carb, 4* adv timing, removed governor, removed fan and shroud and set up as a rope start, and now has a muffler but soon going to finish a new header with a performance straight thru kart muffler. A buddy of mine has turned his ungoverned 212 to almost 6k, and well the 2-speed on mine limits RPMS to around 5000 so I am ok on the safety issues.. And it's got around 1200mi on it, but I want to hit about 65mph at least.

The stock head gasket appears to be approx .010 and it has a dished piston. The ports are very smooth unlike the Flatheads I have owned, so I don't think I will be porting it...

Here's what I am planning
Billet rod and flywheel
Head shave
1.3 rockers
Springs.
Bigger slide carb

Now the questions;
How much can I safely shave the head without running into clearance issues, and reliability issues?
Will I need to get shorter pushrods after shaving the head?
What length rod should I get to use with the stock dished piston?
What length and weight springs?
What size crappy Chinese carb? Is 22mm ok..? Is 24mm better? As my intake is only 22mm...

 

[FirePowerMinis]

22mm Chi-kuni is a proven choice
Rocker adjusters will allow shave without issue
Longer rod that puts piston above deck allows you to take some/all of the lip of the dish off, making it nearer a flat-top.
But, a new flat top is cheap and easy.
Black Mamba JR suits this combo well.
Port seems fine farther out, but the bowl and short side are not. Should curve, not be a drop-off.