OK, I gave a bogus answer the first time because really, are you going to pedal around something that weighs in excess of 1000 lbs (instead of a 40 lb bike) just because of dust and weather?
In addition, it all depends on how resourceful you are. If the donor car and donor bicycle are rotting in your back yard already and you have a welder and other tools and can fab then the price could be close to zero; and if you have to buy and hire everything out the price could exceed $20,000.
And in addition to that, who's to say if I compiled a comprehensive list of what would likely be needed, that the prices I have access to are anywhere near the prices you have access to?
Is $0-$20,000 a helpful answer?
P.S. Just found pics of Mighty Boys- cute! Would you even fit in one? I probably wouldn't.
However a Tempo hacked into a ute would look similar...