Here's my 2 cents FWIW:

How often are you going to be welding at full amperage? I would gues
very infrequently... so you will very rarely pull that kind of current.
Also, welding is an intermittent load... so, you can get away with less
current capacity, cause you aren't running continuously. And, anyways,
70A is plenty... you're not planning on welding at full current while
running a big lathe taking a .500" DOC, with a load of wash in the W/D,
the electric stove boiling spaghetti on every burner, and every light
in the house on, right? I'd suggest work with what you got if you can't
up your service easily. Get to buildin'!