I'm 99% sure that's what you want. I came up with that number too (I guessed on the prefix tho--wrong, it turns out).
I took the number for the complete truck from the diagram you cite, and found it in section 15 of the 1970-1986 book. It showed a part no. 8002-T60, which is just the coupler arm (no knuckle, thumbtack, etc). So I searched thru some other parts lists for similar trucks and found 8002-T70 listed as an assembly. There is a picture of that assembly on this parts site: https://traindoctor.com/service/lionel/7900to8010.php, so you can see if it looks right.