I am installing a BB heater core in a former small block car. Are the two clips that hold the actual core in place the same for the big block, as for the small block? I know the cover and the core are different, which I have but I am having a problem with the clip closest to the passenger side, thanks.

I just finished doing the same conversion and had no trouble getting the clips to work on the BB heater core.

One of the SB clips will work, the other needs a slight modification to fit as the BB tubes interfer with the clip. It can be made to work and work well. Mine did.