Threads on hoses? - Cant figure this out

Google "tube nut", which is what the part on the tubing which screws into the brake hose is termed. You can buy individually on ebay. They come in several thread sizes (and thread lengths), to mix up tubes at the master cylinder and such. Most tube nuts are for 3/16" brake tubing, regardless of thread size. But, early Mopars (~1966-) had a 1/4" tubing and nut from MC (single pot) to distribution block, so be careful when re-plumbing that for a modern MC (must install 1/4 M inv to 3/16 F inv adapter in port).

Around 2000, U.S. cars changed to metric tubing, nuts, and "bubble-flare" ends. Those don't interchange. But, I found the metric tubing is close enough (6 mm I recall) to double-flare and use as 3/16". Also, others found you don't need a special bubble-flare tool since you can use an old dbl-flare tool to make bubble-flares (youtube's).