Chevy Dad with Mopar loving 16 year old son

Greetings, been a chevy guy my whole life and my 15 yo son fell in love with 1968 dodge dart, has big plans some day for his recent purchase. Point is, Dad and son learning together. so here goes. 273 engine compact wheel 9 inch front brake job to get road worthy.

brake drum hold down kits (pins and springs) all parts catalog says for 10" but we have 9", I assume interchangeable? Did the 9" have the pin/spring hold down set up?

what is the part of the brake line between front hose and wheel cylinder called? I've been on different websites like inline but can't seem to find that particular part? any leads? we don't need them yet but wondering in case they are compromised and need to be replaced.

Looking forward to learning and the more pics i see of these mopars the more i think they're super cool. thank you