It is my uneducated understanding that you can fit no more than 2-carb Offenhauser on a stock-sized engine in a Chevy truck 47nd-55st engine compartment. Supposedly, 3 or more carb intakes can fit into a GMC.

Here is Tom Langdon's website (it is slow to load in some browsers):

http://www.stoveboltengineco.com/index2.htm

Tim