I took a look at the Color Head and a Cap Top of a 38" FO printer. Notice the lines I made (Yellow Arrows point these out), this is the last row of nozzles on either side of the head. Compared to the Cap Top it clearly shows enough room/space to cover all the nozzles of the Print Head. It is close, I will give you that but if adjusted correctly The Head will seat properly on to the Cap Top which would pull the correct vacume while the pump in energized producing proper ink flow...
As for who makes the parts and where they come from, I don't know and never had a reason to question this... I do know that when I install the parts I get and make all needed adjustments to the machines they do work consistently with little to no call backs...