[Kevin in NJ]

All the caps appear to be ready to fail.

The upper left of the rear main is cracked.
The other bearing seems to have a separation on the upper right corner.

If you plan on driving the anything beyond around the block or simple local parades then you are taking chances with these caps. No, you can not use other caps. Sometimes you get lucky, but the centers are going to be different causing other issues.

If you want to actually drive this engine places then you had best get the babbitt redone or have a good towing plan.

Have you checked the balance of the engine?

Have you measured the weight of the rods at each end? They should be within a few grams of each other. How close are the pistons in weight? On the factory line the rods were made to a weight +-1 gram at each end. The piston and rod together would have been within 4 grams of each other.
Have you checked the crank dimensions? Is the flywheel less then .002" off center (should be less then .001"). Has the crank been crack checked? Is it straight?
Balance and straightness along with precision grinding to factory tolerances is critical to a smooth running A engine that is not trying to pound itself to death. Ford precision built the parts for the A engine on the line, you have to approach the A engine like it is a race car engine if you want it to run right.