An aftermarket turbo and 3 inch exhaust will give you up the 40% more torque and power and will, believe it or not, use less fuel. But it also puts more strain on the motor and the radiator, etc.A good professionally installed turbo setup is about $3500 to $5000, and it helps if you have a good motor to start with.I have had aftermarket turbos on hilux3l and 5l diesels , and they definately make more power. I have also had overheating problems, at times.Might be cheaper than a new diesel. Bill
That doesn't have a turbo but an aftermarket kit with a VVT Turbo gives more power and Torque Approx 130 kw and 400Nm and costs about $2400 to $3000 plus fitting but the 1HZ-t is already set up for a turbo so is a much better base to work from than the IDI 1HZ Naturally Aspirated engine.
Then add LPG injection and a BIG intercooler and you would be approaching 150kw but pay attention to cooling, a custom alloy radiator and EGT guage and low coolant alarm would be recomended.
All that (minus LPG) would be likely to cost about $10k plus labour (LPG approx 3k fitted).
But you could possibly pick up an 80 series at auction on the cheap with all the bits and bob's you would need for the standard conversion which should give you in the range of 120kw anyway which is a big step up from the 90 odd from the 1HZ.
The other option would be the Chev diesel and auto conversion but that would be about $20k+ as a guess but your looking at (for the L65, 6.5l V8 Diesel) Power / Torque 215 hp (160 kW) @ 3,200 rpm / 440 lb·ft (597 N·m) @ 1,800 rpm.
I would love to see a Chev powered Coaster but I would either only do it my self )if I had the time) or get it done by Brunswick Diesels in Perth as they are the experts and have done heaps of conversions with this engine.