318 Poly in an Early A Body?

I looked into putting an early 354 Chrysler Hemi into a 67 Barracuda. Talked to people that did it. Not an easy fit and definitely not worth it for me. I cant imagine what it would take to get one in an early A.
I have seen such done in a 68 Charger decades ago but what it took?
I figure if it did not come from factory for example, a BB in a 67 A body, or 416 hemi in same, it would take a lot of measuring and maybe cutting and fabbing for it to work as in your example, but you know that. I bet you can go to FB sites for hotrodding and find the answer.
Just because the guy, th OP has never done it and is asking questions does not men he can not figure it out and get it done. Learning new skills is half the fun!