Yup, you're gonna have to go to the larger bellhousing. You don't have a choice. To my knowledge, there's not a 9.5" 122 tooth flywheel compatible with the 318. They changed the crank register size in 1968, on the slant 6 for sure and I believe on the 318 as well, so I think the only way is to get the bigger bellhousing. You'll be ahead of the game anyway with the 10.5" clutch. I'm sure if I'm wrong and there's a different way to get it done, someone will tell you. I think that's right, though.
