When is it good to Sand/ Media blast your car?

Welder's not mobile, its a 700+ lb 1972 320 AB/P that requires a 220V, 60 amp source. That's double the amperage of most household 220 sources.

And unfortunately, it would probably take me until the end of the week just to get my projects to the point where I could move them out of the way to get another car close enough to the welder to do any work, assuming you could get the car to me.

An 8 point cage is not a couple hour job, it's more like a couple days worth of work. At least it would be for me. Even if everything has been notched and fitted, it will have to be mocked up in the car, tacked, removed, welded, re-installed to make sure it fits, possibly removed again, welded again, etc. While most of the welding has to be done in the car, some of it will definitely have to be done outside the car too, as not all the joints are accesible inside the car, especially if the cage is fit tightly to the inside of the car.

Guys that build cages for a living could probably do it faster, but that's not me.

Also, I wouldn't MIG weld a cage. There are places out there that won't certify a MIG welded cage.