I think E-Type were built in Coventry before there was such a thing as MIG welding so I am curious how the various bits of sheet metal that went into making the body were welded together at the factory? Was it mostly electrical spot welders with some oxy/acetylene welding in some places?
Just curious.
By '65 they were using wire welders. Don’t know if they were MIGs but the occasional wires with melted blobs on the end sure looks like it. There was some brass used, but irt doesn’t look as if the used gas welding on anything.
I can’t address your question directly but in Porters book there is a comment I remember. A team of 4 guys at Abby Panels would assemble a monocouque in about 15 minutes. And Abby charged about 17 pounds for the finished product.
That helps explain why they all needed fettling to get them together 
The restorers I know need to be aware of this time line. When they send a bill for thousands of dollars I’ll just explain it only requires 15 minutes, maybe 30 since your guys aren’t experts.,
There was definitely MIG welding on the roof part of my '62 FHC together with pop rivets presumably to position the parts first.
Quite probable. Mig welding dates from the late 1940s.
My car has a few areas where pieces of wire are still there…
Mig welding was definitely around when they built the bodies. My 1968 FHC has some mig welding and a lot of resistance spot welding. Mostly spot welding.
I think that old B&W video of Jaguars being built mentions both spot welding and wire welding as new introductions to the E-type. I can’t get the video reference until I get home.
I’ve seen this on a couple of cars, especially on the IRS cage.
And let us not forget blob welding, which was used on the coupes around the license plate area.