youll find you can use (Y) or (TEE) block fittings or AN (Y) or (TEE) fitting that are usually much cheaper at your local hydraulic hose supply fabricator.
what Ive always done is take careful measurements, on the car Im having the fuel lines built to fit, using a section of old garden hose,to duplicate the route and location,of the AN #8 fuel line a model, , and then write down all the lengths and types of fittings on a piece of paper so I could show the diagram to the guys at the hydraulic supply and they usually have it fabricated to match my specs in under 30 minutes
if theses some threads that are not all that common I bring the fitting Im trying to duplicate, in most cases they have the required adapters or can make them dirt cheaply in minutes.
once you carefully explain exactly what your doing and that your building a high flow fuel system, they build you exactly whats required.
I almost always have easy access to short sections of garden hose because I occasionally run over longer sections with my tractor.