TK ordered his new engine from us. The 175 engine I offer is a 62mm bored GY6, 174.5cc actual displacement. It's a direct bolt-in fit for the Spiderbox, mounts exactly the same as the original with no modification.
Tom after re-reading your last post, I think you might have the fake "200cc" GY6 engines on your mind. The "200cc" GY6 engines floating around the net that are actually 170cc (61mm). They're lying, intentionally fudging the numbers to create confusion and scam up sales.
This all can be very confusing to the uninitiated that might be reading. I wrote a detailed "beginners" article years ago that will help clear all of this up. Explains the relationship between Bore, Stroke, and displacement CC. And has a calculator you can use to interactively see how changing the bore size OR the stroke length will affect overall engine size.
https://www.**********.com/tech-cent...er-calculator/
Hmm... replace the stars in my link with the BD name to access the article. Then plug in 62mm bore and 58.8mm stroke to calculate the exact CC size of our 175cc engine.