Itll be -4 you want, not -6 and definately not -8!!

The fittings you posted pics of above are not the correct fittings to screw into the bodies, you want them without the shoulder.

With regards to nylon ptfe pipe, as already said you cant clamp down on it it is only intended for the correct fittings.

Use the rubber lined braided hose, that can take -an (aeroquip) fittings or jubilees.

Dont use the hose finishers, theyre shit!!