Engine Mechanical problem
1969 Jaguar E-Type 6 cyl Two Wheel Drive Manual 86890 miles

this is a 4.2 double overhead cam engine. there is interference between the valves and the pistons because the cylinder head was machined too much. Is there a thicker gasket that can be used to bring back the clearance and if so do the torque values change if used? Is there another remedy?
Thank you