The 70 Coronet Quarters will not fit unless you rebody the entire rear end of the 69 with the 70 pieces.
Meaning you'll need both quarters, the 70
tailpanel and the 70 trunk lid..
Also, the rear lower trunk gutters are different
on a 70 Coronet vs. 68-69. You would have to
salvage them from a 70 coronet donor car to get
it right.
I don't know if you can salvage those w/o screwing up the tailpanel in the process...
so you might end up needing 2 donor cars plus
the quarter panels to pull the job off..
To say the least, rebodying the rear of the 69 with a 70 would be a tedious/time-consuming process at best.
I guess I have to ask....
Why would you want to do that?
Just to say you did? Well. OK...
Better still, if you have NOS quarter panels for the 70, sell them to AMD or better still, trade them for ALL of the 69 Sheet metal you need to do your 69. Quarter panels, rear w/s cowl, full trunk floor, trunk extensions, rocker panels, floor pans, outer wheel houses etc...
They make everything for a 69 and they are very nice parts.
One of the factors why AMD isn't making 70 Coronet quarter panels is because nobody has
ever come forward with an NOS one to copy....
True, it isn't the main reason, but it's a factor
none-the-less.