Pete, besides the different lengths, the cowl ends are also different. One type has threads starting at the end and extending up the rod approximately 2". That rod would have two round rubber washers, two flat steel washers, two lock washers, and two hex nuts. This hardware soft mounts the rods to the cowl mounting brackets. The other type rod has a carriage bolt head formed on the end, threads traveling up the rod from the carriage head about one inch, two round rubber washers, one flat steel washer, one lock washer and one hex nut. If you have or could borrow a copy of the Early Ford V8 Clubs 1935-'36 Book, all of this and much more is covered in detail.