I have a 1973 Dart with 10" drums all the way around. Right now the bolt pattern is the small 5 lug 4" pattern. I know that Chrysler had 10" drums on some of their other cars that had the big 5 lug 4 1/2" bolt pattern. Would it be possible to swap with a set of drums that has the big bolt pattern?

I'll be anxuiously awaiting a reply also. I think what you're going to hear is that you could use B Body 4 1/2" bolt pattern drums but will have to change the upper control arms to accept a larger ball joint.
BUT I did read on an internet siste a few years ago that an AMC
Gremlin 10" front drum would directly interchange on the A body.
I don't know if you would use the AMC wheel bearings or the Chrysler ones (don't know if they are interchangeable).
Sure would like to hear some knowledgable replies!

Find a 73 to 76 V-8 Dart, Duster, Dart Sport & swap the parts over. The 73-76 A-Bodies came with 5 on 4 1/2 so the parts shoupld swap right in. I think if you do a search in the FAQ area you may get all the info you need. I know it is on here somewhere.

The drum brakes from '67-'72 B-bodies and '70-'74 E-bodies can be used on the A-body with a change of the spindle and the UCA from the same vehicles. These are 10x2.5" drums with a 5x4.5 bolt pattern. If you are really daring these cars also had 11x3" drums.

So the center hole is going to be a different size? Is there a chance there could be a bearing that would fit my spindle and the inside of the drum from the B or E bodies?

Nope.