What they said. The 326 shares no parts (well, possibly the carb, definitely the points/condensor/cap/rotor, but not the underlying distributor) with the SBC, and the bellhousing bolt pattern isn't the same either.
The 326 is part of a Pontiac family of engines, but I forget what the other members are. I was an Cadillac and Olds man. I can tell you about Cadillac engines from the 365 in '53 to the 425 in '80 or so. And, from experience, I can tell you about the one-year-only 1964 429ci, because I owned both a '64 convertible and a '65 Fleetwood, at the same time. In the parts books, they're the same engine, but I know different.
Or the Cadillac 390 ('59-63): the '59 has a bypass filter (cartridge, no drain, use a suction gun); 1960 got a full-flow spin-on below; 1963 moved the dist to the front of the engine (a lot easier to service) and larger main brgs.
(I owned a rare, one-of-975 1959 Eldorado Seville. You read that right. If anyone is truly bored and wants to know more, waste fifteen minutes with this page
and the link off it to a pic of mine. I wrote that one up years ago -- like six years, probably.)
Useless info like that, I can remember. But I really don't know Pontiacs. I'd have to use Google to refresh, and you can do that as well as I.
Disturbingly, I am finding that I have begun to forget even the useless stuff. I can remember that the rings for a 1960 Corvair (another one-year-only engine: 140ci, where '61-3 were 145ci) will also fit a certain year Humber Super Snipe (3.375" bore). But I can't remember if the '64 Corvair (last of the Earlies for styling, first year of the larger 164ci engine has a generator or alternator. The cut-over year was right there. I used to know this stuff. But middle age is arrived, I guess. And my next pair of glasses will have to be bifocals, dammit.
(SeaMonkey spellchecks inline, as I'm typing. I just learned I can add words to its dictionary: RMB on a word it's called out as misspelled, and the menu item is right there. Just added "Corvair".)