Spectre Chassis the same?

Odd question. But thought I'd throw it out there for my cheapo EBAY shopping. Are Spectre Chassis the same? The 550, 750, and 1100? Are there significant differences between them? Or just is it a different motor paired with the same frame?

Thanks

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JMK is correct...a 750 Spectre may have more in common with other contemporary 750s than with larger (1100) and smaller (550) siblings....other than the possible paint scheme:)