68 dart GTS 18 rims question

..the pirate jack rear kit I’m assuming has an adaptor flange or redrilling... haven’t installed it yet...
as far as a spacer for the back spacing, I don’t think we can run spacers over here, I think they’re illegal to run..so if I got 18 x 8 with 5.25 back space(I do see a lot of posts about 4.5 backspacing? ) and run the 245 40 18 I should be right ?

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