What's the deal with the Poly 318

That is going to be a TIGHT squeeze, especially in and early A. There is a reason Chrysler went to the LA when the A body got a V-8
It will be a little work to make it fit but I have a 66 valiant with a 540 predator headed mopar in it and I know it can be done. I will post pictures of the progress and build on here soon.