Spark Plugs for 76 Dodge D5N 318 LA engine

Good afternoon, having some problems locating/identifying correct spark plugs for 76 Dodge D5N fitted with LA 318 engine. When I do search on
the NGK site, the plugs currently fitted, - A6F S, come up as a blank - these are a 14mm tapered seal plug. Checked out some sites for plugs but they
show plethora of plugs for the LA 318 engine including those fitted with sealing washer and reach of .750. The plugs taken out are .395 from end of thread
to centre of the sealing taper (think this is referred to as the 'reach'). Was hoping some kind person with owners manual may be able to give me
the original fitment and I can try to cross reference it to a currently available plug.

Thanks in anticipation - Patrol01

Patrol01,
My Dodge books are showing for LA 318-3 the following info,
Champion F10 spark plugs, 18mm tapered seat gapped at 0.89mm (0.035 thou).
This is for engines with electronic distributors.
Yet, yours are a 14mm tapered seat?
Somebody else may have a different take on it.
Dave.

Hi Dave-64. Thanks for the reply - I didn't even think of measuring the width of the threaded area given all of the sites I found for plugs for the LA 318 listed them as 14mm. Will pull one out and check. Some of the sites had multiple plugs with reach from .380 through to .750 along with some with tapered seal and those with washers. I know very little about these engines at moment and am doing all the research I can. Mine does indeed have the electronic distributor.

14mm will be the washer type seal and the 18mm are the taper seal. Cars and light truck engines are 14mm and the heavy trucks are 18mm

Thanks Hardtopman. Do you know anything regarding the front axle bearing covers - mine are 8 sided nut and am wondering if they are left and right hand threaded - have not been able to source a socket for them as of yet. BTW they were 18mm taper seal.

I’m probably stating the obvious, but if you fit plugs with a longer reach than those presently fitted, it might pay to turn the engine by hand for a few revolutions to ensure the pistons don’t hit the plugs.

Hi Dieseldog. Thanks for the comment - went with plugs that had same reach as ones already fitted.