Because I want to make life difficult (or I'm optimistic about success) I'm still considering swapping the stock 318 LA engine with a 400 B. I picked the 400 B block up from my machinist just to check the fit. Using the engine mounts from the B100 van it came from, I was able to get it to fit fairly well into the A108 compartment. However, I would love to get people's feedback on what I need to be wary of before proceeding. See attached pictures of how the engine mount bushings are lining up and the space in the front and back.
Furthermore, I realized that I can probably swap the transmission tailhousing/adapter from the A108 to the 727 tranny so it mates to the 400 B and properly hangs under the frame of the van plus is the right length so I don't have to shorten the drive axle. What do you think? Am I crazy?