It's true that the 216 and 235 heat chambers are different sizes. Consequently, it is not possible to bolt a 216 intake manifold to a 235 exhaust manifold. If you want to use the 216 2x1 intake you have and want to bolt it to a split stock exhaust manifold, you will have to find a stock 216 manifold to split.

Luckily, it is not that difficult to find stock 216 exhaust manifolds at reasonable prices. You might be able to find one on Ebay or here in the swapmeet. There might even be a few fellow 'bolters that have been tripping over one in their garage and are ready to get rid of it.

Good Luck