If you have hardened valves/seats then low lead is not a problem. You can mix the two 93 and 100 and get 96.5(approx)
On another note.
Don't want to start an arguement over this but I have heard/read that 10.5 CR (iron) and 11.5 CR (aluminum) is the max "SAFE" CR to use 93 octane. It may run fine on the street but not the best to do if you hammer it, you could have issues. Better safe than sorry.
