Rear end rubber brake hose replacement

I noticed the difference as well. I just recently removed the 7.25 rear from my '75 Scamp, and the rubber hose was part of the brass block - as opposed to my '68 Road Runner which the hose screws into the brass block.
On my Scamp I am using the brass block that was included with the 8.75 I purchased. You could use the older style brass block on your '73 rear and get the hose that srews into the block.