my old man has gave me a welder now the problem is it a mightymig 105 turbo im guessing its no good for the build as its 105amps. the problem is the torch is missing the neck fires wire fine etc and has a gas bottle inside. so do i look for a new torch and practice with it on some off cuts or stick it on the auctions and add money towards something better

Depends what you want/need to weld. I have done plenty of car stuff with a 90a Clarke mig. That was rather good on panelwork. But also did a fair bit of chassis work.
105a should be ok with 3mm steel without any issues.

As to spares, plenty available on the bay. I think weldequipe is the well-liked seller.

what he said. did most of my chassis on a 100 amp cebora. only got the 150 amp clarke when i fried the cebora. (running 3 data centre cooling fans against the open case to improve duty cycle - lasted a hell of a time too.)

If it's in good order, it should be fine for a Locost build. I recently borrowed a Sealey 110 A machine to build a go kart in 3mm wall box section and after a bit of practice it was possible to get good penetration and tidy welds. Since bought a Clarke 151 which doesn't really weld much thicker, just carries on for longer before it needs to cool down.

ill treat her to a new torch and tidy up then. ill get practicing on the go kart 1st see how it goes.
question about the gas use it or not?

You'll get a better weld with gas and gas (non-flux) wire is cheaper however, some say that if you're welding outside in breezy conditions, gasless wire is better. Personally, I just turn the gas feed up a bit.