Hmmm, it would seem to me that its highly unlikely that the frame, such as it is, is broken. Even on my race car there are only few stress cracks that have had to be welded up. And thats on the left side, where the panhard rod mounts to the shell. What is most likely the case, is that the reinforcing plates just above the rear shock mount has rusted out. This has happened on all but one of the 140's that I own have come through my shop. Its not unfixable, but you do need at least access to a MIG welder and some sheetmetal skills. I've made this repair many, many times. One used to be able to find replacement shock plates, but I havn't seen them available for a long while. I've taken to making my own.

This was a serious flaw in the design and was remedied on the 74 model year, when it was basically a first gen 240 without the front struts. It doesn't necessarily mean that there is severe rust elsewhere. The other common places for rust are under the battery box (duh), in the rocker panels just ahead of the rear tires, the lower corner of the rear tire fender lip, (catches all kinds of crud and rusts out), and the front inner fender, right behind the hood hinges. Its a rare 140 that doesn't have some rust in one of these places. All are annoying, but not that hard to repair by a competant sheet metal person. I've done this on probably 6 or 8 140's. But then, I also recently cut off and welded on a new section of frame on the front of my racing 140 from where I nosed it into a tire wall. So my idea of whats doable is probably a little more than what most sensable ppl would even consider.