I apologize - I wasn't clear in my question.
"This is only emergency backup planning for one of my build candidates; I'm still trying to choose which."
... to put a cage into ... and then finish building.
Yes, I have several _well_ under $500 vehicles as race car candidates. I'm not at all familiar with BMW, but this one drives quick, and the front end is tight. It's the first BMW I've driven. And I kinda like it. But not too much. It has an auto tranny, I like manual (that's what I thought it had), and if I'm going to build this one, I'd like some confidence about engine replacement - just in case, as I got it used.
So I didn't really explain, other than the comment about the older GM engines 'you can put anything into anything' idea.
It seems reasonable for a chassis type to have bolt points in the same place, engine type / tranny agnostic, so that different engines can be put in; with maybe just different bushings and brackets for them. But I don't know that.
I think your answer is along those lines, and gives me reason to still consider building it. This is one I still do not have a title for - just a municipal bill of sale, so I can't (yet) title it to drive it on the highway.
There's plenty of replacement drivetrains for other candidates, from manufacturers I'm more familiar with, that are easy for me to get, and for cars for which I have a title.
Once I choose, I'll have to thin the inventory.