can any one help me to identify what beast lay under the hood of my 52 canadian built 1314 model 1/2 ton truck.The casting numbers on the head and block haven't matched any numbers that i have found to date...leaving me very stumped!i intend on rebuilding this silent beast but don't know what part to order for it.

The following cat numbers are as follows.
head# 3695451
block# 3695408

I am not sure if its is even its original engine and have know way of knowing from its original owner who has long past.

would greatly appreciate any or all help in this matter