You might want to consider membership of either the TSSC (Triumph Sports Six Club) or Club Triumph (which I am a member of), if you haven't already, they are a great source of spares, info and advice.
Here are a couple of links:
https://www.clubtriumph.co.uk/...
The R-Tech 180 will be more MIG than you'll ever need and good advice from @tigdlo re gas.
I have had a Cebora 130 for the last 30 years or so and I've restored a GT6, Morris 8 and a Rover SD1 Vitesse, amongst many other car repairs, and i've never found it wanting.
I'd recommend getting a...
As @Burdekin has already alluded to, a mass of 1kg exerts a force due to gravity of circa 9.81 Newtons.
If you dangle 255g on the end of a 1m arm, you will generate a torque of very close to 2.5Nm (or in old money, about 1.85 lb.ft).
The thing is with torquing up of nuts and bolts etc, is that...
Sadly, not a skill I ever learned. That said, I learned welding using O/A at school and have gas welded ally, albeit a VERY long time ago :)
Are the two techniques that far apart :dontknow:
I'd certainly love to have a try.