-most vaguely modern combustion chambers have a 'squish' band around the edge of the combustion chamber. This gives a static clearance of 1mm or less between the edge of the piston and the head. However, under dynamic conditions, the piston to head clearance is a small fraction of this, certainly less than the gasket thickness (the con-rod stretches....).
- This means it is normally a really bad idea to fit a head gasket with smaller holes in it than the bore, as you will get interference between the piston and the gasket.
-you can't really cheat and relieve the squish area; you will rob the engine of both power and efficiency.
-a bigger (too big e.g. 92mm) head gasket will create a pocket for detonation and screw up the c.r.- both bad things
-you really need an 89.25mm (or whatever the new bore is) head gasket.
hope this helps
cheers