My brother and I both bought 8-port Hyper 21 engines. Mines is the standard version and his is the race engine. The internal differences that we could see were that the crank was fatter and the main bearing and block are appropriately sized for it. The piston/sleeve, connecting rod, and carb are all exactly the same. Another key difference is the fact that his engine came only as a non-pullstart while mines was a pullstart. I've since converted mines into a non-pullstart engine (really easy to do and it only cost $9) but have not run mines. Oh, his has a nicer cooling head, too.
If you do get the 8-port race engine for your Savage you will find that you will not be able to start it because the Savage requires a pullstart engine or some way to start it without access to the flywheel. You could always try to find someone like me with a brand new starter assembly for a Hyper 21 engine who is willing to sell it. Also, if you do get this engine, I would suggest that you install it into a different car, break it in using a bumpstart, then install it into your Savage. That is because the pullstart on the Hyper engines aren't all that strong and trying to start a green engine will almost always break the string or spring. Once broken in it should be fine.