Dynaco MKIII: new power cord

[tubes rule]

I want to replace what appears to be the original power cord on a pair of MKIII's that I just bought. If I replace the two wire with a three wire cord where should I connect the ground or should I not ground it? Has anybody done this mod?

 

[cogsncogs]

If I replace the two wire with a three wire cord where should I connect the ground or should I not ground it?

To the chassis, near the power transformer.

Wayne