More power 80 series

Manual or auto?

Intercooler and 3" exhaust will make a big difference and will add some torque, turning up the boost a bit will also.

Baz.

Diff ratios or tyre sizes.

I'm not an expert on Cruisers, is the td a turbo? If not a diesel with over 300k on it and adding a turbo would place a lot of stress on the old engine.

If you will be doing mainly towing then change diff ratios or get smaller wheels.

I would suggest you get some headers, it will make the engine breathe better and give you more time to rev out in each gear before having to change up keeping the engine in the power band.

Other than that you should tow with my 4.2 diesel GQ and see how yours compares to mine. They are not racing cars when something is hooked on to the towbar but will get you there every time.

Barnesy

6.5lt chev diesel or install a 15speed to get you going on those hilly bits. By your description the engine is running fine and all the problems are lack of torque down low.

Turbo whiz maybe able to suggest a different turbo to bring on boost earlier.

Have a good one

If its a factory turbo 1HDT then my suggestion is to get the no boost fuel adjusted on the pump,very simple job to increase low down power.

Matt

I have a 94 with aftermarket DTS Turbo. We wound up the fuel and it increased performance by up to 10%. Your best bet is to get it tuned on the dyno to make sure you dont overfuel and make it go bang!
I tow a 6.5 mtr boat long distance at 95 - 100kph with no worries. Any faster and it will start to send the temp gauge up. I am also running bigger tyres, 285/75r16.
There is not much more you can do aside from putting it on gas.