Anything but reload and penetration. No way should a vehicle as fast and mobile as a Jackson have 338 near pen with the regular rounds or 325 far pen with HVAP. Same as SU 85 with its 286 far pen and 312 near pen.
What would you suggest to replace it for? Reload would made it even stronger (as it was before).
Current alternatives:
-30% reload, -30% scatter
+30% armour, -10% reload
-20% reload, +20% speed, +20% rotation speed, +20% ac/de-celeration
-+10% armour, +25% HP, +35% sight range
+20% speed, +20% rotation speed, -20% reload
-25% reload, Weapon rotation+ 35%
As far as the Su85 goes, more rotation rate and/or a more forgiving moving accuracy penalty would always be nice. It already has good sight, pen and reload.
The Allies have to contend with Axis having Panthers stock, lethal tank hunters with great armor, and OKW has the Tiger II as a stock unit. This means the SU-85 and M36 Jackson must be able to contend with both of these effectively, as it is the allies strongest defence. The King Tiger is highly effective in it's Spearhead mode, and the Panther is the undeniable Dive champion. If the SU-85 and M36 cannot shock these units, then the SU-85 and M36 themselves will fall prey to the vehicles they exist to counter.