Have some screenshots for you on how the SU-101 looks like with the 122 mm M62-C2 gun for you. But before...
I was showing the screenies to Jingles that brought me a cup o'coffee (Bless him!) and I asked him a couple of questions as when it happened what I'm about to tell you is a bit far off my alley. I didn't always pay attention to general changes in the game back in the day and specially about the Soviet TDs as I always had a fling with the German TDs instead.
Basically, and like I mentioned yesterday, the SU-101, tier 8 had the 122 mm M62-C2 initially, which is basically the same gun as the IS-4, a tier 10. Wargaming decided to remove because it was too OP and as a big surprise its back now.
Game Balance is a complicated thing and I'm a bit apprehensive about this, in the other hand, I started grinding the Soviet TD line a couple weeks ago and wont lie that once I fully upgrade the soon to be mine SU-101 will have a evil W. Riker sh** eating grin at the prospect of pounding the enemy teams with it.
I also made a gun stats comparison on how different the SU-101 gun is from the IS-4's:
122 mm M62-C2
Reload time: 11,50
Aim time: 2,9