Which Engne to replace a worn out 4.5 petrol

[JuzGU]

Hi guys,
I am looking at replacing the engine in my 99 Gu wagon, it currently has a 4.5 petrol in it but the motor is on its way out.
It is set up for dual fuel and i mostly run it on gas but the fuel consumption is still rediculously high.
On gas i use around 23lt per 100 kms
On Petrol i use around 30lt per 100 kms

It is my work and play car which i drive every day and tow a work trailer which loaded weighs around 800-900 kgs.

On the weekends i either tow a boat weighing around 1.5 tonnes or a caravan that weighs around 3 tonnes, towing either one i go backwards on any incline.
I dont want to sell the car and buy another one because i have it set up just how i want it.

I am not sure whether to replace the engine wth a rebuilt 4.5 or to put an ls1 into it, i know the ls1 conversion will cost another 5k minimum on top of the price of a 4.5ltr but the fuel consumption will make up that cost in 6 months.

I wanted to get some opinions on what would be the best motor of the 2 for towing and for fuel consumption.

Thanks

[JuzGU]

Forgot to add it is a 5 speed manual

[chev_1973]

How many kms have you done?

Mine does 300 km city driving on 82 litres of lpg.

[nissannewby]

Is a td42t conversion out of the question? Going to the ls1 will be good but you will be paying an extra 300 odd dollars for rego and possibly increases in insurance. The ls1 will prob use less fuel while towing and in general i believe but still not quite as good as a diesel.

[TD_Wagon]

Just go all out with a 6.6L duramax! ha ha

[eddietrx]

Go with a common engine I am in the process of doing a VH45 conversion and everything that can go wrong will. Although it is starting to come together now. If you are going to pay someone to do it expect to pay 15k min

[97_gq_lwb]

Personally i would reco the 4.5
would not even consider using any form of gm junk ever again .

[JuzGU]

It has done about 230,000 kms

A 4.2 diesel isnt out of the question yet, but i have been told the motor and conversion will cost about 15K, and i can do the LS1 for about 12K, a friend is going to do the engine rebuild and help me do the engine conversion.

What sort of fuel economy would a 4.2D get?

6.6 Duramax, i wish, but i cant tow around a fuel tanker

My biggest worry is that if i reco the 4.5 and end up with a bit better economy but still not much towing power

[4by]

Think I second the vote to reco the 4.5. Could do some head work and get some more hp. Otherwise build it to suit a turbo then your laughing. Ive done engine mod swaps and it always costs more and things don't work or come together easily. As said before don't forget extra insurance and engineers costs.
Might cost a bit less if you can keep some parts that are still okay with the 4.5 rebuild.
230k isn't heaps, mine has more ks. My gas consumotion is about the same. What makes you think it's on it's way out?

[ansaha]

Gen 3 mmm power
Cheers