That price is certainly not bad. You might be able to find one a bit cheaper, but at more risk. I'd be comfortable with the one you linked to.
Vendor reviews, like stude13 said, is a good place to look around. You'll feel more confident when you've made your choice.
And most of us would be reluctant to recommend a particular bike (or engine) because what works for me might or might not work for you. But that engine will fit almost any 26" beach cruiser or mountain bike as long as there's about 15" or so from the crank to the top tube. You might even squeeze it into a 24" beach cruiser. I managed it on an engine with the same dimensions. It was close, but it made it.
You'll have fun. Now go for it!