I know NGK TR-55s are the preferred plugs but which version?

 

iridium plugs always.

 

V power for me.

 

Iridium resists gap erosion so they will last longer making them possibly preferable for a car that sees mileage. A plain plug is just fine performance wise but the gap will wear and get wider much faster than it would with a platinum or iridium plug, probably need to consider changing them by 20K miles.

 

Plain old Autolite 103 plugs here.... I change them out every spring even if its not needed....$1.50 a plug, can't go wrong