72’ Ironhead frame engine fitment issues

[ExplodingCoffinEmporium]

Bit of backstory, my buddy bless his ambitious heart had this 1972 IH, the trans took a shit, he got frustrated and was talked into altering the backbone to accommodate an evo engine. So he cuts off the backbone, which he no longer has and installs a very solid piece of tubing to allow evo fitment. I acquire this frame from him later on, and have now come to a point of deciding what to do with it. I really have no desire to throw an evo in it, I have a 77’ engine sitting around however. It would seem like quite a waste to find another IH backbone and cut it off to replace this one. Would it be feasible to install the 77’ engine and weld a new top motor mount into place? I know the 77’ oil pump is a fitment issue for older frames, or so I’ve heard. I guess just looking for some thoughts, thank you