If you decide not to take the $3K-$4K plunge for the correct 450 wheels seek out a set of 3766075 15x7 rims. They look similar and can be had for $250-$400 for all 4 of them.

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70 Road Runner 383-4 4 speed FJ5 & black guts
70 Charger R/T 440-4 4 speed FJ5 & white guts