When I started putting together my Death Korps army, I began with the armor. Since I picked up the Apocalypse sets back when they were released, I had 3 Leman Russ and 3 Basilisk kits already on hand. I also picked up a few Forge World goodies, including the Bombard, Salamander, Vanquisher Turret and Exterminator Turret. Not being a fan of the standard Leman turret, I decided to upgrade it with extra detail.
The first thing I did was extend the Battle Cannon. The standard Battle Cannon is too short for my tastes. I prefer the Ryza pattern that the Death Korps uses. Simple enough conversion: Cut out the mid section of the barrel and replace with styrene tube of similar diameter. No fuss, no muss, and you get an extra 3/4 inch or so of length. I could have removed the muzzle at the end of the barrel and made the gun look even more like the Ryza variant, but I was doing it on the fly and didn't think about that option till well after the fact. Oops.
The next thing on my to-do list was to trash the regular plastic hatches. I do not like the high profile at all. When GW released the Steel Legion kits (so I believe), they included metal replacement hatches that were much more flush with the top of the turret...so much so that the cupola was almost entirely gone. Since the Forge World turrets used this style, I was able to replicate it in styrene. Using a compass to measure, I was able to cut various thicknesses of styrene sheet for the cupola and hatch. The bolts were cut from lengths of octagonal styrene rod. The handles were also cut from lengths of round styrene rod. The periscopes were cut from thicker styrene sheet, then beveled to match the Forge World turrets. It was a LOT of tedious work, but worth the effort.
After the hatches, I went at the glacis plate. The standard glacis on the Leman Russ looks kind of doofy. Again, with Krieg as my baseline, I went with the Mars-Alpha pattern look. I knew that modifying the rear/engine deck was out of the question, but felt that back-filling the forward hull and glacis plate would be simple enough. I was able to cut sheet styrene to fit behind the mounting point for the forward sponson, and then add some strip styrene above the new plate to make it look more solid. In the case below, I used a modified Space Marine lascannon to replace the Imperial Guard lascannon. The lascannon was extended a bit, then glued into place. Around the base I built up a blast bag using green stuff. Octagonal bolts were added afterwards. On another Russ I used a Heavy Bolter instead of the Lascannon.
Finally, I added a bit of extra armor on the relatively naked turret side. Again, sheet styrene cut to shape, surrounded by octagonal bolts came to the rescue. For that extra level of detail, I added a slightly thinned down Aquila. As before, the idea was to up-detail the tanks to be a better match to the Forge World turrets.