Hmmmm....I dont know if my Hooker headers are 5903 but I ordered them from Summitt specifically for my 70 Charger RT.
They are Hooker Comp 1 7/8 ceramic coat and they were very easy to install and fit very good with very good clearance. My car is a 4speed,Lakewood Bell,mini starter,RB block,Stealth heads with large 1.06 torsion bars.

I dont think I got the only set that ever fit cause lots of guys have had success with them.