If you have the double humps already then yeah they're probably worth it. The compression will be significantly higher with the 64 cc chambers. Several years ago I had a similar engine to yours with 882 heads. Kinda like yours the cam was a bit too big. I changed to doublehumps and it matched better with the cam. It was definitely better. A few years after that I switched to dart heads and it was another big jump in power. Basically what I'm saying is yes the doublehumps would be better, but aftermarket heads would be even better. If you can do it for $100 plus gaskets, that is mighty tempting.
Also, you might want to check that the doublehumps have accessory holes. Mine were 461 heads that didn't have accessory holes. They worked fine but it was a bit of work making brackets for the alternator etc.
One last thing, you should pick up a vacuum gauge. They're cheap, probably $10 and a great tool.