Regardless what you do it will cost you, the question is how much.
I went through the same thing with my 1991 80 series carby petrol 12 months ago. My 80 drives like your 105 except I use 1/3 more fuel than any diesel.
LS conversion was quoted at $20K plus.
HDFT recond engine, the cheapest I found was $12k not including install.
I already have F & R air lockers, rear draws, wheel carrier, bull bar etc.
I spent $6k on my 3F to rebuild and a few upgrades which brought the old girl close to 400NM but I still lag in the HP department 135HP.
I still struggle on steep hills with the Jayco on the back but not as much as b4, but my old girl will last me another 10 years plus and she will go anywhere 4wding.
The most important thing for me was reliabilityfirst and foremost, availability of parts and cost of parts which are dirt cheap, as we do remote trips and that's what I got. Couldn't be more happier.
Yep, my mates have $50k plus 4wds but they are also in heavy debt and can't afford many trips away
The cash I didn't spend for a diesel or LS conversion is being spent on extra holidays
If you want a fast car buy an early xr8 or a ss.