You could build it to stock specs. Then all you would have to do is find some 100 octane leaded fuel and you would be good to go.

Or you can take the advice of people who have been through all this and have a motor that has 50 more HP,runs on 89 octane unleaded and no over heating.

PS, open or closed chambers still 72 cc's (unless heads are62's then about 75 cc's)