Build a hypothetical post-apocalypse bicycle

Smallfurry is politely and modestly avoiding the obvious, his fat and long bike will be exactly what Mad Max would choose to ride (in MovieWorld). Has the optional custom weapons rack been ordered yet?

For real world unkillable bikes, check out Cuba, their bikes are even older than their cars.... I sent over a box of old bits to some of their racing guys I have ridden with, they're the best bits in the land!