289 vs 302 how to identify
Around 67' and 68', it's hard to tell which engine a car would come with. The only real difference between the two engines is 1/8" of stroke. The 289 has a 2-7/8" stroke, the 302 has 3".
As stated, the 289 crank has '1M' stamped on it's counterweight, while 302 cranks are stamped with '2M'.
Casting numbers on earlier blocks are on the very bottom by the starter... and are often covered by grease. (I believe it's that side, could be the other, but I think I'm right) Anyway, they are on that lower rearward section of the block down by the oilpan.
Casting numbers start with a letter indicating the decade the part was produced.
C = 60's
D = 70's
E = 80's
You get the idea......
This is followed by a number indicating the year within that decade the part was produced.
C6xx = 1966
C7xx = 1967
C8xx = 1968
You get the idea.......
The 302 OFFICIALLY came out in 1968, but since the only real difference between the engines is the crank and rods... They even use the same pistons. It's hard to tell which displacement cars made around 67' or 68' ended up with. I've seen 289 blocks with 302 internals, and 302 blocks with 289 internals.
BUT, if it's a C6xx or earlier casting, and hasn't been redone, it is definitely a 289. If it's a 67' or 68', you'll want to double check it. If it's a 69', it should be a 302. The assembly line tends to pull whatever it takes out of storage when stock starts running low... so the unlikely could happen. 70' or later will definitely be a 302.