Iggy:
Just Car insurance is cheap... but I spoke to a few people and they don't really like how Just Car handles things when something has gone wrong... THey will not allow you to choose your own repairer, you gotta get 2 quotations from their recommanded repairer, then they choose the most competitive one to hand your car to... Also the agree value of Just Car is pretty low compare to other insurance company...
They do insure modified cars though... but the excess is A LOT more than other companies... I think they just trade your Excess price for the Premium fee... although the premium is 1250 (for my case, I am 27 years old, no accident history with rating 1, agreed value of 57000), the excess is 1750 dollars... so if something has gone wrong.. the total bill is 3K for that year and you don't get to choose your own repairer and the repair job has only 3 years warranty...
I am now with Shannons, although I am paying more (220 per month), I get to choose my own repairer with life time warranty, excess is 600 for me with agreed value of $72000 and people don't have any problem with Shannons when it comes to "a problem"... but if it really happens, that year, the bill will be around 3K as well (same as Just Car)... Shannons will give a lot better price after you turn 30 years old... 3 years to go for me, but another 5 years for you though...
I would prefer Shannons because I have spent fare bit of money on my car already and I am sort of betting extra 4K at Shannons (compare to Just Car in 3 years time before i turn 30) to get the difference of agreed value which is $15000 if something goes terribly wrong... Insurance is like that, it is like gambling... and of course you would try to avoid using it as much as possible. This is just the way I look at my car since I am going to keep it for a LOOONNNG time...
These two are the ones that will insure modified engine... otherwise RACV and GIO (if you don't change headers) will be a good choice for you if you don't want to do too much mods...
Best of luck mate!
cheers,
richie