road race engine...

see what rocker arm specialists thinks about the shaft mount rockers, they will give you the straight shot check who mfg is, Hughes does not make
I'd also check with B3racingengines- he will also give you the straight shot and if the geometry is correct with those shaft rockers
On the Hughes cam, look up the cam in theHoward catalog AND cross reference the lift and duration with the Howard lobe list- see what you are getting
https://www.howardscams.com/sites/default/files/lobe list email 1-20-2014.pdf around page 8
If I was getting an endurance/ road race cam Mike Jones would be my go to with his Indy cam and GM R&D dollars into that application
The resulting inverse radius profiles are superior to Everyone elses
really easy on the valvetrain and no bounce on the close and they rev well
Also many threads about problem with HR so check it out
I see that Howards has a timing chain with an Iwiss chain (but maybe only for chevy) that's the chain you want if you go chain- check Manley and other quality vendors but I'm with YR on a gear drive