The 983 stock needs one or two easy modifications to fit the 981t.
1) A little free-hand Dremel work with a 1/4 burr-ball, inside the reciever pocket of the stock, to clear the lifter spring pins. Removing maybe 1/32 deep x 1/8 wide x 1/4 long both sides. You cannot see these from the outside.
An RFC member has a nice photo of this if you need to see a pic.
2) You need to order a trigger guard and screws from Marlin because the 981t has a molded in TG and the 983 has a separate metal TG. Tell them what you are doing so they send you screws (a little longer) for a wood stock.
3) Optional..The 983 stock has only one takedown screw. The 981t has two. Your choice if you want one or two. I recommend order the trigger guard with both screw styles from Marlin so you have a choice. The front TG screw is a wood screw on the 983 and a 10-32 machine screw for the 981t.
I just have a Simmons 4-12 on my 981t. It was less than $100. Man this gun shoots good. I like to shoot the CCI HP subs with it and watch the bullet fly to the bullseye.