Found it in one of the books I always carry with me... "Chevy Inline 6 engines" 1929-1989.
Based on the numbers...It says the 3837004 is '55-57 235... The "H" in the block number also verifies its a 1957 chevy 235 truck motor w/140hp and should have a 3sp transmission. Hope that helps some

Thanks,
-Paul