Spark Plugs

I started pulling plugs on my new toy and note that it has E3.42 plugs. I know nothing of E3 plugs. Are they worth keeping/continue using? Are they compatible with a Mallory 6AL box? Engine is the original Q Code Cleveland rebuilt 5k miles ago with 9.5 CR, original heads with SS valves, Comp Cams 218*/218* @ .050" w/ .494" lift, Offenhauser 360 intake, Holley 750 DP (that I am swapping out for a QuickFuel 680 w/ vacuum secondaries) and Mallory Unilite distributor. What standard plug would you suggest if I decide to swap out the E3's? Thanks in advance.

Expensive plugs. I'd keep them is they look ok. If you were to replace them I'd look to some NGK's as the older go-to Autolite 25's quality has faltered since they started making them in Mexico and China.