My FS is a bone stock 2hp model and, with the exception of a 16 tooth front sprocket, tops out in the mid 30's at the expense of low end power but that's what pedals are for.
I hate to say it, because your bike looks minty & unmolested, but if you're going to make a fast bike, you've got one of the best platforms to do so already.
Super strong tube frame construction with a wide, durable swing arm that can take up to 2.75in tires, lots of room around the carb area, the wide pedal clearance gives you so many options with that bike. It's an E50 Puch, so performance mods are nearly endless, easy and inexpensive. The engine is stupid-simple and very robust.
Detachable tank is a great feature 'cause kitted bike are thirsty so it can easily be replaced with a larger capacity one. Or do a top tank conversion if you're conventional.