Howdy DaveM,
About the only leather vest I have seen that looks right is the John Wayne style. Frankly, I suspect that it is very authentic, but we've all seen it so much that it looks right. My recollection of the contemporary photos I've seen is that the vests were most likely fabric.
I agree with Abilene that lapels look best. Also, consider 4 pockets - 2 below and 2 above.
Those are my thoughts, for what it's worth.
Rev. Chase