motor vin

[bruceman1968]

C8F181490 V0425TDR

You have a discrepancy with your numbers. Your going to need to get the casting date code off the block. (see pic below for location) We can tell that your engine is not original to your truck based on the numbers provided so far.
Truck motors did not get partial VIN's till the mid seventies. You have a partial VIN on your motor so it can't be a 67-72 truck motor and therefore not original to your truck. Your suffix code identifies it as a truck motor and not a passenger car motor so the block must be later than 1975. (TDR the T indicates truck) Suffix codes do not tell whether the block is a 2 or 4 bolt.

C8F181490
C = Chevrolet
8 = 1978
F = Flint assembly plant
181490 = Unique ID number of the truck the engine was originally installed in

V0425TDR
V = Flint engine assembly
04 = April
25 = 25th of April
TDR = 71 350ci,255hp, Auto
TDR = 72 350ci,175hp, Auto
TDR = 80 350ci,170hp, Auto

This is where we have a discrepancy. Your partial VIN is for a 1978 truck, but I can't find the TDR suffix code being used in 1978. It could be that the online websites and the reference materials I use have omitted the listing for some reason. Or could be a miss read on your part, or a miss stamp from the plant.
You have a 350ci from the late seventies, but to find the year you will need to check the casting date code on the block. Should be a letter followed by 2 to 4 numbers. (ex D28, D208 or D2078)
Please recheck the suffix code(TDR) and the second digit of your partial VIN(the 8). Although most likely you have them correct and the TDR suffix code for 1978 is just missing from the publications.
Definitely check the block casting date code. Then we can determine what year your 350ci is. See pic below for location.
Casting numbers always trump Stamped numbers.