Hi Harry
Sorry for the non-definitive answer, the Chevy 216 was in production long enough to have a number of changes. Your link to the one on e-bay is an example of one of those changes if you look at the back side you will see that it had TWO discharge holes to the block while the war time 216 as used in the CMP (I've seen) had a SINGLE larger discharge. There are also differences in the length of the shaft and the size of the pulley.
I have photos illustrating these differences that I will find and post. The pictures will help spot want you need to be looking for.
Correction, the back plates on the water pumps can
Not be swapped. But check your engine if it has ever been replaced it may be the later two hole design. Also many of the pulleys can actually be pressed off and swapped for the correct one.
Matching the pulley size is very important if you are running the CMP 6 blade fan, the many of the civilian pumps have a much smaller pulley which spins the fan much to fast, noise and danger of failure. Take a look at the pictures on my 235-261 conversion page and you will see some of the pulley issues
http://www.canadianmilitarypattern.c...ifications.htm
Edit- Add more pictures of back of two styles of pump.
1st Picture both water pumps
2nd Picture later style with gasket
3rd Picture early style with later gasket
note the mounting bolts don't line up.
Side point of interest, you need the later style pump if you are going to do the pump conversion on a 235 or 261 to the lower pump position.
Cheers Phil