Here is a paragraph from the Recumbent Cyclist News EZ1 review last year:
UPGRADES: It’s possible to lighten up the EZ1 by ordering an aluminum seat back ($90 retail, J&B part #67455 — see J&B note at end of article), aluminum seat lower struts ($12 retail; J&B part #67457), upper struts ($12 retail; J&B part #67456) and alloy handlebars ($70 retail; J&B part #67349). This might save two or three pounds. Lighter wheels and tires are also possible. An EZ Sport 20” fork (J&B part #27664 black or #27665 silver) will also fit, so you can convert to a 20”/20”. If you are going to make all of these upgrades, you should probably just buy the lighter AX model.
It seems to me that the seat base on the EZ1 steel vs. alum was not interchangeable due to square tubing size. You might want to check that before you order.
Bob Bryant
http://recumbentcyclist.blogspot.com