kent glendale

That's going to be a tight squeeze but doable .
The large down tube will be a challenge .
A 2 stroke is , i'm afraid , your only easy option other than electric.
Advice : Drill no holes!!!!!!!! Buy a slant head , short intake kit.....

China girl looks doable, but you will need to order an oversized front motor mount or build your own from a car muffler clamp. You may need an offset intake manifold or make your own with some heater hose from a car. Some things just can't be determined until you attempt the installation.
A four stroke will not fit in that frame.