SharpMark, good questions. I didn't do anything for vent to filling, i based the design on an original '48ish chevy that had the tank under the bed & pieces of the filler neck are from one of those. I tried to make it look as if it were factory, even though they weren't avaiable. When i filled it for the first time i was disappointed how long it took so i will experiment will the filler neck angle, rise etc. I think it is a gravity thing and not venting.
We made a plate to seal a chamber under the tattersfield and have 3/8ths(?) copper going to it, supply from the water pump and returns to the thermostat housing. It is cold here and i can start the engine up with little choke and it'll quickly idle - i use the choke more as a throttle for the higher idle.
I am having a problem with the carbs getting stupid with flooding at high vacuum, when i close down the choke the vacuum gets high enough in the carbs so (i think) fuel gets pulled from the main wells. As long as the engine runs and you open choke as normal there isn't a 'problem', if you shut the engine off after brief idle fuel will dribble out the throttle shafts. Its an interesting problem and may be an inherent design issue with the 'tube' type carbs.