3701946 is a low pressure 1953 truck block.
"The presence of the oil pump indicates to me this is a factory engine., but not a babbit, and maybe low pressure in a 216?"
?? all 216/235 (and, 261) engines had an oil pump
You might be referring to the oil distributor on the middle of the block under the middle of the manifolds? That would have been used on low-pressure 216/235 engines.
Pre '68 Dave (or others) will have to confirm about babbitted rods being used through 1953 on which engines (car/truck, 216/235).
1953 was an oddball transition-year for Chevrolet 6-cylinder engines.
