I did mention that a handful of M4 Shermans got the M2 gun. Definitely the T-6 prototype and a Sherman M4A1 named "Michael" that was the first shipped to Britain under LL. Michael had also a pair of fixed .30 MG in the lower centre hull, like those fitted to the M3 Lee/Grant series. So when I said handful I really meant that. Think of them more as pre-production trial vehicles, I very much doubt that any saw service. So no need for any modification of British/US/Soviet vehicle notes.
A clip of Michael, refitted with the later M3 gun:
As for US Lees, I have seen clips of them training in Northern Ireland and those clips had both the M2 and M3 armed Lees in the same unit. As only one regiment (2 x 3 company battalions) from US 1st Armoured used Lees in NA, photos of US Lees are scarce. Incidently the 1st Armoured had some of its M4 Shermans shipped to the British just prior to El Alamein and had to do with M3 Lees.
One of the few photos of Soviet Lees that I can quickly find appears to show 1 M2 armed and 1 M3 armed Lee, taken around the time of Kursk. From memory, others that I have seen show the M3 more often, though I could not swear on that.
en.wikipedia.org
So in the end due to the mixing of M2 and M3 guns, which used the exact same rounds, in the same units, it would not be possible to make an accurate but generalised rule. Like
jrv, I would be inclined to treat all except "Grants" as having the higher TK.
As an aside the original SL and later ASL conversion U2 "Sweep For Bordj Toum Bridge" used reduced US TK. Partly for older ammo and I suspect some M2 armed Lees. The US 37mm M6 gun (37LL) as used in Stuarts and as AT M3 guns had particularly bad early ammo. The early M74 AP round got 36mm penetration whilst the later M51 APCBC round got 61mm! So with the early round a TK of 9 would be justified while the latter round well earned a TK of 11.