Just to add to the confusion about the engine: as Steve posted, a 235 engine was not listed as a Regular Production Option for a 38xx truck in 1949; however, as John posted, just about anything could be ordered by a customer or by a dealer. Also, it would not be uncommon for an original buyer's recollection to be unreliable and/or a one-owner truck to have had an engine replaced over the years (and somehow everyone has forgotten about the change).
As John has asked, the block and head casting codes (and date casting codes) would be helpful in identifying the engine-year; and, the engine serial number would be quite helpful in identifying the application of the engine (the RPO and size of truck, if 1949).
Here is some information about the locations of these codes. 
