Well Im not sure about 1100's but 1300's and 1600's definately have different pistons as jerm has mentioned. And no the cranks are not all the same, the 1600 crank is alot bigger, hence the extra inch in height of the 1600 block.
If I was you, and wanting to eventually put a V6 in it, I would say, stick with the 1100 for now, put the bigger carb on it and maybe some cheap extractors (there is always some on trademe) and just enjoy that until your ready to do the V6 project. All up to you though
Welcome to Oldschool, happen to have any pictures of your car?