TheHEMI.com

Have a 54 (I think) 331 Industrial Hemi and need to know what plugs to run in it.

I bought the engine as a "short block" and it had AC-Delco R44XLS (3/4" reach) plugs in a box along with it.

1956 MOTORS Repair Manual shows that there are some different plugs that were used in the Chrysler products with V8 engines. Displacements were not stated in the manual.
Some being; Autolite 4GS-150, or 4GS-170

Would the R44XLS plugs be OK for "street" use? I can pick up new ones at NAPA

I'm told that '54 was a changeover year, do you have a casting number?

That said, this is the advice that I'm being given on picking out plugs:

If the exhaust ports are round, use Autolite 86.
If the exhaust ports are oval, use Autolite 65.

I hope this helps!