Weaver rimfire rings have been good for me. They are about $10 and sometimes can be found at Walmart. I like the Leupold Freedom scopes. Also Clearidge Ultra RM is a good scope. I have a Burris Droptine on a Marlin 60 and is a good scope for the money.

 

Congratulations on two excellent finds. I can't help much with the 990DU, but for what it's worth, the 980 was Marlin's first bolt action in 22wmr. Production, according to Brophy, began in 1962. Believe the "J" identifies a 1966 manufactured date.

My 1967 model has a Weaver Classic V-9 with Warne 7.3/22 steel rings.

 

Both are dove tails, prolly 3/8 ths. The bolt gun will require higher rings. These will work fine for the semi auto

https://www.amazon.com/Leupold-Rifl.../ref=sr_1_4?dchild=1&keywords=leupold+rimfire+scope+rings&qid=1620738271&sr=8-4

And these for the bolt gun https://www.amazon.com/gp/product/B001HN5H7K/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

As for scopes, go with an adjustable objective or side focus , vs fixed parallax. And variable magnification vs fixed. And SFP vs FFP. Iff you're shooting paper, then 12 X plus if you want to see the holes, if you're hunting, or shooting tin cans 7 X is fine. No illuminated reticles. Objective lens diameter 36 to 44 mm.

Lots of choices, dont go cheap, but no need to break the bank either. Vortex , Mueller, Burris.make good mid price scopes

 

I use Weaver Classic V-16 scopes (4-16x) on most of my rifles. Here are just a few of my Marlins. (which are all magnums..22mag or 17hmr).

Signalman

 

If you don't want to spend a lot of $$ but still have a decent optic set-up, check out the Bushnell Prime 3.5-10x36AO that Natchez has on sale for $75.99 (1/2 off price). I just got one last week to put on my 1966 Glenfield/Marlin Mod 20. I used Warne 1" 7.3/.22 Med steel rings. The bolt just barely hits the bottom of the ocular when being removed for cleaning. I just put a small piece of electrical tape where ghe bolt hits. No problem, Solid set-up and real decent low budget optic. :bthumb:

 

If you don't want to spend a lot of $$ but still have a decent optic set-up, check out the Bushnell Prime 3.5-10x36AO that Natchez has on sale for $75.99 (1/2 off price).

Thank you for spending my fun $. Two of these inbound 'cause that's a screaming deal.

Sent from my Lenovo YT3-X90F using Tapatalk

 

I put a Leupold rimfire scope on my Model 80DL with no serial #. Bought it 2nd hand 50+ years ago. It sure is clear, and that helps my old eyes.

Have a blessed day,

Leon

 

Nikon rimfires are good ,I own 4 of them.I would like to put a weaver v 16 on my 22 mag,cant find one.Everybody brags on the weavers