If you are after a budget car with a hard top then maybe G Force cars in Perth might be your answer, useing the Toyota crown chassis.
There has been abit of discussion about this kit in here lately and the consensus seems to be that when it comes time to sell you will be at a definate disadvantage, I am not sure about in Vic but I did look at this kit about 6 years ago (I had a toyota crown in the shed) and Queensland regs said it would be reregisted as a rebodied toyota crown.
Here is a link to there site
http://www.gforcesportscars.com.au/index.html
Another popular kit that can been done on a budget is the DRB kit useing LH torana as a donor, from what I know you can use the 308 engine if fitted with straight LPG.
I dont know if they offer a hard top though.
Here is a link to there site
http://www.drbsportscars.com/
You could probably get 1 on the road and registered with out the shiney bits and useing an under car exhaust and LPG for a reasonable cost.
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Cruising in 5th
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Never be afraid to do something new, Remember, Amateurs built the Ark: Professionals built the Titanic.