The 351-C was in production from 1970-1974, so there are few block casting
numbers to look for. Note that the 351-C is NOT the same as a 351/400-M
or a 400-C. The first table just shows casting numbers. The second table
shows technical information on the various blocks.
1 This is my block.
From the table below, note that the 289, 302, 351W, 351-C, 351/400M and 400-C all have a 4.00" bore. The displacement difference comes through the stroke. However, there are other significant block differences that are not apparent from just looking at the bore and stroke. Within a family, there are some similarities, but not complete similarity. For example, within the 335 family there are differences in the crank centerline to top of deck change. This results in differences in the intakes, connecting rods and pistons. The 351-C has its own heads that don't interchange with any other block outside the 335 family. The 351-C 2V, 4V and Austrailian heads, as well as the 351/400M and 400 heads, can all be used on any 351-C block as long as the intakes and exhausts are compatible. However, they are not all equal in performance. See the heads discussion for more information.
Since the bore spacing for all the small blocks (including the 351-W, 351-C, 400-C and 351/400M) is the same, you can get some interesting interchanges if you are willing to perform additonal machining, such as boring some additional water passage holes. A 351-C head can be put on a 351-W, called a Clevor. TRW sells special Clevor pistons. The canted valves in the Cleveland heads mean you can't use the Windsor pistons. The Boss 302 was, essentially, a 351 Cleveland, 4V head put on a 302. Any 351-C head can be used on a 302 with some adjustments to water passages (I have forgotten exactly whether you plug some, drill some or both) and special pistons.
The 400C has a taller deck height than the 351-C so it can accommodate
the longer stroke. Since the 351M is basically a destroked 400M, it also
has a taller deck height. A taller deck means wider too. You can see that
the Crank Centerline to Top of Deck dimension for the 351/400-M and 400-C
are nearly the same as the FE family (390, 427, 428) and 385 family (429/460).
Therefore the 335 family is often considered a "Big Block" engine. The
351/400M and 400-C all require a "big block" bell housing. However, the
351-C has a smaller deck height and needs a small block bell housing. So,
the 351-C is part of the 335 family, which is thought of as a big block
family, but it has many attributes of the small block 90 degree V family.
Since it is smaller, there is much less weight in the 351-C so the HP to
weight ratio is very high.
1) This is for 1971-1972. Starting in 1973, height is 9.503"