Combustion Fan Questions??

I am working on installing a Weil Mclain Series E Boiler. I want to use a combustion fan ran off an aquastat. I will be putting the fan in the ash box where the draft door bolts up. My questions are as follows; 1) How many CFM fan should I use? 2) Where should I buy such a fan? 3) Do I still/should I use a Baro and/or MPD in the system?
I really don't know much about the boiler I got ahold of Weil McLain and nonone could tell me anything. They said they would look in their archives for any information for me. They only knew that it was from the 30s or 40s. I feel like it is in excellent condition so I'm not worried about the age at all.