Thanks!
I am thinking the obvious thing is to keep the sockets the eyes come with, and try to join them into the pony head but the trick is getting the pony's viewable surface to merge properly with the eye assembly such that it looks right....in that end, I was thinking to use super-sharp precise xacto blades (scalpel blades would be better but don't have access to them right now) and cut a complementary angle into both the sockets and the pony so the whole thing fits properly, and then glue in place. Even if I can make the cut precisely on both parts without mistakes, then there is still the issue of the glue being applied just to the right place and not fouling the eye movement.
It's a precision deal. I don't want to use clay or paint so it'd be really exacting...I'll need clear eyes, a steady hand and lots of good luck to pull it off! Or a better plan, haha.