HELP - specs on Edelbrock #8003 please

[eSJayDee]

Going from a stock 4bbl to 6 pack on a 440 & the kickdown linkage is too short.
Edelbrock makes a 1/4" rod extension (part #8003), but no where can I find the specs.
Tried emailing for specs - they don't answer tech emails.  Tried calling tech support hotline & get recording "due to high vol, we're not answering the phone at this time."  ARGH.
Anyway, how much length can you extend using this rod & how many threads per inch.  (Pic looks like 20, but my rod (they do specify for Mopars) is 28.)
Thanks.