Shovel Short & long reach spark plugs ?

The fins inside the rocker cover are milled off. I think the change was in 05/78

I meant to say inside the U on the rocker covers. That is visible with the heads on the bike.

I think the long reach plug was introduced in 1974, but no clue which date.

How do you tell if it's a long or short reach plug w/o looking at the codes?

Yes, and I would like to know the answer...

I know, but it was no activity on the thread for long and I was too curious to wait any longer.

Anyway, thanks for the reply, good thing to know.

What is your source? If you have any tips for a good Shovel book it would be appreciated.

OK, that's a good source I suppose!

Never seen that and probably never will so keep posting questions. I enjoy reading them but I seldom know any answers...