MSD Coil & total timing help

You are not saying what dist. you have. Does it have vaccumn advance? If it does, is it hooked up? leaking? or bad diaphram? If it does not have vaccumn advance the amount of advance is controlled buy the bushings that stop the weights, you may have to change them. The speed at which the mechanical weights are applied is controlled by the little springs attached to the weights.
To only have 24* total advance something is not working right inside the dist. That is where I would start looking.

Jack