Conveyor Belt Number at Foundry
CON4 = Conveyor 4

Engine Block Cast Date Code
L131
L = 12th letter in alphabet = 12th month in the year = December
13 = 13th day of the month = 13
1 = last digit of 1961
Date block was cast on, December 13th, 1961
This engine probably went into a 1962 year's model passenger car.

Block casting Number
3769716 = 1958-1962 235 cubic inch

Engine Serial Number
FI214B
F = Flint, Michigan - Engine assembly Plant
I2 = 12 = 12th month in the year = December (Sometime the letter I (eye) die stamp was used as the number 1 (one).
14 = 14th day of the month = 14
Engine assembled on, December 14th, 1961
1961, B = Regular, Powerglide transmission RPO 313 = Regular Production Option 313, Powerglide engines used Hydraulic lifters
1962, B = Regular engine, Powerglide, RPO 313

A high percentage that this engine was:
Cast in Flint Michigan on, December 13th, 1961
Assembled in Flint Michigan on, December 14th, 1961
Made as a straight six cylinder 235 cubic inch engine.
A Powerglide transmission was mated to it.
Has Hydraulic lifters.
Was installed into a 1962 model year passenger car.
Its painted orange.
1961 Passenger car GM Vehicle Information Kit or restoration pack.
1962 Passenger car GM Vehicle Information Kit or restoration pack.

Tim, I looked at every passenger car resto pack from 1950 to 1965. From 1957-1964 they use code B for RPO 313 Powerglide transmission.
1965 code is FM

1954 Chevrolet 3105 Deluxe Panel Truck
w/Factory HYDRA-MATIC