With no mods the assembled EQ heads are good to about .515 lift with either the 1.92 or 2.02 valves.
Anything over that demands the Hughes retainer kit that gets it up close to .600 and there are longer valves and aftermarket rockers available that can put it way up there.
I used a .501/.512 cam and it was HIGHLY recommended that I use the special retainers to eliminate the chances of a retainers hitting a stem seal.
I also used the Hughes (310lb open) valve springs because the ones that come stock on the EQ heads are pretty weak as referenced on Magnumswap.com
Talk to our member magnumopar and he can set you up with the springs, retainers and locks that will be safe.
What you definitely don't want is for the retainers to smash the stem seals (at over .515 lift) or the springs not pulling the valves closed at higher RPM's and letting the pistons and valves introduce themselves to each other.
At our lift we could probably get away with the as assembled heads, but it was just too close for comfort to me.
I didn't really want to spend the money on the better stuff on my daily driver either but just couldn't risk it.