Zabbs22

Does anybody happen to know what the wheel offset in mm would be for a stock 14x 6 steel rim on a 68 delta 88. Current tires are 225/75-R14 and the car has drum brakes . I know the pattern is 5x5 so I’m assuming this are 14x6 rims . Trying to put a much larger wheel with slimmer tires on so I need these numbers for the tire Calcs. Thanks

the set up I want is 18x8 with 245/40-18’s front and back