Proper spark plugs for 1974 3.0l 140 hp

[Redtruck12]

Having difficulty figuring out what spark plug to be using on my restoration project. Engine has not run since I have owned it but has been completely gone through/rebuilt
boat is a 1974 Duo Vagabond
3.0l - 140 hp
model #21404
serial# 2829054

i am questioning whether the plugs have been changed for an improper number over the years?
i didn’t want to just assume that they are correct.

plugs that were in it we’re champions-RV8C
when I cross reference that # I get ac delco CR43 T

my original paperwork says ac delco CR43N? Which is a gasketed plug
BUT this head is a taper plug style!

I an an more than a little confused
It is possible?? The head has been changed over the years?
Can anyone shed some light on what might be going on?

 

[Alumarine]

Perhaps the head or motor has been changed?
The tapered plugs you need might be AC-R43T or NGK BR6FS

 

[Bondo]

Ayuh,...... Most all Chevy boat motors, up to 1996 run the AC Delco MR43T spark plugs,.....

 

[Redtruck12]

Thanks for the responses. I had my local marine supplier run the engine number and they confirmed NGK BR6FS

crossing the AC CR43N came up to NGK BR6ES ( very similar part number)
problem resolved

Thanks again for for your input