I saw this on FB, a shop installing an oil tank..did this cut..
Is it really necessary ?

Looks like a some reinforcement was added to the rear as well. Did it mention whos tank was to be used?

???

If that is Ben’s / MB911 tank, no extra cutting is needed. I have the first one he made for sale and a version 3 that was made a couple months ago. Both tanks fit in my 70, 71 & 74. I have heard the door support in later cars can interfere with the tank but it doesn’t on mine. Remember the early cars had the same chassis as a six but mid year and later had changes that no longer needed to fit a six at the factory. Still, I’ve never seen the need to cut into what looks like the suspension console.

That looks like the same stiffening kit I have on my big six. It is from Brad Mauyer.

The longitudinal stiffing kit from Brad Mauyer has a tab that will interfere with the installation of a stock oil tank. It interferes with the oil line coming out of the tank. I had to notch the re-enforcement to get it to clear the line in my car.

It may be worse with an aftermarket tank. I have only tried the stock tank.

Clay

Is that cut to clear the oil hose or to get the in tank past it?

I know for sure it's not a DWD tank just looking at the welds, (I have a DWD tank) and I'm pretty sure Ben's tanks fit better than that. The DWD tank is a bit bigger than a stock tank but everything is spot on in the stock location, it was tight but went in without issue.

My guess is it's a Patrick tank as I heard they were a bit rough, at least the early ones, but I admit that's 3rd-4th hand info.