Head Gasket Replacement on 1982 KZ100 Spectre

I am replacing my head gasket and I was told the motor was bored out when I bought it. I measured the cylinders and got 2.906" or 73.8124mm.

I think the stock cylinder size was 70mm, but I am not sure. How do I figure out the CC of the motor to make sure I order the correct head gasket?

If a 1000cc bike:
pi * (R^2) * stroke * # of cylinders

3.1416 * (36.9 *36.9) * 66 * 4 + 1129cc
Hope got that right! LOL

I think the Wiseco company makes good oversize head gaskets.