You might want to get in touch with these guys:
H&W Machine Repair & Rebuilding - Parts and Service for the Metalworking Industry
They've been in the rebuild business for over 35 years. They will sell you any Bridgeport parts you can think of. They will also walk you through any tough spots. They also have a set of instructional videos on their website. They are very knowledgeable and easy to talk to. I haven't had to do a full head rebuild yet, but over the years I have purchased parts from them and gotten installation tips. Whenever I need a part for a Bridgeport these are my go to people.
I have no association with them other than being a satisfied customer.