I noticed the underside of Superbird trunk lids have the cutouts for the spoiler mounts.

As Supbirds never came with a spoiler, is this just the lid that was available during the time of production?

Do they all have the trunk lid with the cutouts?

Yep.

I take that as a yes on both questions.

Next one, is it a standard 70 RR / GTX lid?

YES, SAME AS A 4-DOOR BELVEDERE OR SATELITE

The Sport Satellite and GTX models have holes for molding on the back edge of the trunklid. Other than that the lids are the same on all 70 Plymouth B body models,except for the station wagons.

At the beginning of the model year the rear spoiler (J81) was not an OPTION so all early decklids do not have the cutouts.

When the spoiler was announced 10/69 Chrysler would've already had the engineering figured out & new "cutout" decklids ordered or in the "system".

there will always be exception (actual or imagined) but:

8/69 to mid-10/69 NO "cutouts"
mid-10/69 thru 11/69 EITHER
12/69 to 7/70+ "cutouts"

I imagine Chargers are the same also,no cutouts on the early ones?

Yes, all '70 b-bodies will be in the same "boat".

E-bodies have additional issues with an added spoiler in the spring.

thanks for understanding that i meant the trunklids are the same, but some models as noted did have molding holes

yes, i have gotten trunklids off of 4-door cars that did have the spoiler cutouts

i dont recall seeing sbirds without, but never went crazy trying to document that fact

sbird production ran from october thru december

Thanks for further clarifying Tony.