Technical Offy Chev 216 dual manifold question

I have an Offy 2 carb manifold for the 216 in my 50 Chevy Styleline Deluxe. My problem is the Rochester B carbs I have don't fit it. They're about 1/2 a stud too wide in the base holes. Is there a different base size on these carbs for different cars or are they all the same? Also what's the difference between the Offy 216 and 235 manifolds. Is it just the carb stud spacing? Is my manifold set up for the earlier Carter carbs that came on late 40's 216 engines?

 

Can't believe somebody doesn't know this.

 

Sounds like your carbs you have are from a 235. The 216 bases are smaller. The difference between the 216 and 235 intakes are the carb mounts and the heat riser also has a different bolt spacing in the front(closest to the engine) i think.

 

Thanks. I figured there were Model B Rochesters with the smaller bolt spacing but all the ones I've seen around here are the larger ones. I haven't measured the one that's on my engine now yet. I saw a 54 pickup today at a car show for the scouts with a 235 and he had the same Offy manifold I have near as I can tell with a pair of Carters on it. The B was used by GM a lot more on 235s than 216s I think which would explain all the larger bases I see around here. I think 50 was the about last year for the 216 and the first year the B replaced the Carters. And in 50 the 216 was only for 3 on the tree cars. Powerglides got the 235 to make up for the parasitic drag of the automatic tranny.