How to change my small bolt pattern to big bolt pattern

Changing my Small bolt pattern to Big bolt pattern. The reason is because they have more wheel options. Please let me know the cheapest way to do this. Can I get new axles? And should I get disc breaks from a 73-76 Dart? The wheels I want are 18" 5x4.5 and the wheels I have our 18" 5x4. Any info will help. Thanks,

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