So you're standing at the parts counter.....

Just tell them you have a 1970 Challenger 426-8 and need wiper blades.
Even if ya gave a slant six 3 speed. You know what ya need tget don't.
Most everyone working there is a moron.
Or just do like I do and Rockauto it for less, or look in ya Mopar parts book, etc.
Only you know what ya need.
Back in the 80s- to mod 90s my wife driver was a FE5 and then repainted FC7 Challenger built 340(solid cam ported intake/heads, headers manual cut outs 18 inches back from collectors ) built 727 (Fairbanks converter built) 8 3/4 Dana Power Lock with 391s in the 8 3/4.
It always eat Fox Bodies for lunch that ran NOS. And though they were faster.
She never open the hood so word on the street and her work was she daily drives a Hemi car with 340 badges.
We have quite a bit of One time at Band Camp Stories