The 9A1 engine in the 981 is superior to the M9x engine and needs less help. It scavenges oil from the heads to ensure the bearings never starve for oil.
The major issue is too high oil temperatures. Add 3rd radiator and use good oil and then see what the oil temperatures are. LN engineering recently came out with a 9A1 oil sump for the purpose of increasing the oil capacity to control oil temperatures. Any additional sump will reduce ground clearance.
Other things that will indirectly reduce oil temperatures are: GT4-style side air scoops will help keep the engine bay cooler. Coating and wrapping the exhaust helps, too. Run in Sport or Sport Plus mode as the coolant is regulated at a lower temperature (105C vs 90C). The car uses cooling water to oil heat exchangers on engine and transmission, so cooler water temps will decrease oil temperatures and dramatically shorten the time the oil temperatures are high once in cool down and off the track.
After that, invest in better brakes, brake cooling, and suspension. Rear sway bar is usually the first mod to reduce understeer. Mods to increase negative camber front/rear are next. People use wider tires/rims with spacers to get more grip on the track.
One key to making the engine last is to never go on track with a cold engine. Oil should be 160F, especially on a new engine, due to very narrow piston to (aluminum) cylinder wall clearance.
I have no knowledge if this fits a 981, so you are on your own.
Doesn't look like it, sadly. Plumbing looks fundamentally different in terms of inlets and outlets. 4 holes on the engine side for the GT3, 2 for 981.
The only one that might fit and might be bigger is from the 991 Turbo. It's a different part number at least and it's plumbed the same way but hard to say what the difference is or if the bolt pattern even matches.