Nick - Some resource searching makes it look like your exhaust manifold may actually have casting # 839130, which corresponds to 1940-46 exhaust manifolds for ALL Chevy 6's except for COE models.
The casting date L20 decodes as: L = November / 2 = 2nd day of November / 0 = 1940
Your intake manifold 839279 is indeed listed in my 1929-46 Chevy Master Parts Catalog as fitting 1940-42 Chevy's, ALL except COE. The later manifolds had a different casting and part number.
Looks like you have a matching set (?) of 1940 manifolds.
The correct gasket between to two manifolds is GM# 838290, 3-1/2" x 4-5/16" according to my same resource.
You can get an
NORS gasket on ebay (for a good price + shipping), or order one from one of our various vendors, like
Filling Station Part# FS-62.
All that being said, Kevin makes a valid point about what carb you have/intend to use when considering to use these or go with a later 235 set.
