ok ive been oh here before with this question and still am working on it here is every single number i have pulled its a 454 sittin in a 66 chevelle and i cant find out what year the engine is from to get the correct water pumps and ac setup's so i neeed some help badly so the numbers are
in back of block--826-74 ... GMT12
off the side---3999289
front of block under cylinder head which if i could read it i would have no problems but its almost completely gone so here is what i think i might be reading---To530rw
then under the W of TO530RW is a c with allot of blank space then mabey comes a 37
so it reads like this
T0530RW
C ......37
so i know its from the years 72 threw 79 from running the 3999389 number but i cant find out what year exactly so i now have the head numbers from inside which are
driver side---GM12T
J22-75
passanger side----D-3-73
GM6T
353049
some one on here told me it could possibly be a 75 or 74 but i have no clue how to run the vin numbers i only found out how to do the cast number so if any one could possibly do me a huge favor and give me a hnad on figuring out what year this 454 is from i would appreciate it
thanks for any one can give me some help sorry this post is so long also

According to "Chevrolet by the NUmbers" the 3999289 block was used 72-75 on all passenger vehicles, and in heavy trucks till 78. check the casting date at the rear of the block at the top of the bellhousing flange, near the casting number.Should be a 3 digit number, month, day and year. Third number is the last digit of the year,i.e. 2=1972 etc.
Steve

Its 1972-1975 454. U really dont need to know exact year as all parts are interchangeable between the years 1970-1990. It sounds like its a 75 motor because the last casting date is 75. But there is a date on the back of block pass side about same location as casting# is. If its in the car good luck reading it.

front of block under cylinder head which if i could read it i would have no problems but its almost completely gone so here is what i think i might be reading---To530rw
then under the W of TO530RW is a c with allot of blank space then maybe comes a 37
so it reads like this
T0530RW
This is the most important of all the codes you have. Once you get these down 100%, we will know what it is from.

Right now, the C leads me to think you got a engine from a Chevrolet truck but without the exact codes, can't be certain. NOTE--The suffix RW does not seem to exist, can't find it pointing to any 454 (or any big block) in any of my sources