Block number 3769717 = 1959-1963 261
Block Casting date C 1 2 = March 1 1962
Engine serial F0313LB
F = Flint, MI plant
03 = March
13 = 3th
LB = (in 1961) = base engine on the CLS60 truck
Head casting: 3836850 = 1954-1963 261 head
Head casting date: C 16 9
C = March
16 = 16th
9 = 1959
That would be a real nice engine in your 1953 truck.
- use your 1953 clutch assembly and u-joint cover/assembly
- use your 1953 generator
- use Pre '68 Dave's water pump re-locator (and your 1953 water pump)
- if your 1953 truck has the 3/8" fan belt groove, it should match up OK with the 261's harmonic balancer's belt-groove.
You can use the by-pass oil filter.
The 261s usually had a different design/style thermostat. You can use the thermostat housing and thermostat from your 1953 engine.
Others will correct the above, and/or, provide additional information.
Will you be 6v or 12v?