What was the last year for the slant?

Thank you, as soon as I read the word bolt ons I decided I wasn't touchin this thread
CORRECTION: I decided I wasn't touchin this thread unless somebody else had already explained it. :D

As much as I love to share my knowledge, I've typed the very same explanation that you Bill have provided, too many times to too many people on too many forums and I really didn't feel like doing it again. Especially considering I type all day for a living while answering phones :banghead:

I think I'm gonna write one really good article on this subject, as well as a few other slant subjects and save them so I can just copy and paste in the future. :glasses7:

Do you mind if I use some of you're explanation Bill? Cause there were a few things in there I didn't know and I really liked, paticularly the part about why they stroked the 170.

I do gotta ask though Bill, you made it sound like they made a different head for the RG block but retained the G block's port and valve dimensions. I held the understanding that both blocks shared the same head. So is there an RG and a G head? Or are they interchangable?