This is a list of units from version megamek-0.35.25-windows that are listed twice (the exact opposite of missing units). I have noted the differences where there were any (some appear to be identical). I went through all inner sphere units (didn't do clans yet, doing the i.s. made me go cross-eyed). I hope this will prove helpful.
UNITS LISTED TWICE
Inner Sphere 'Mechs
Light
Mongoose MON-68: This unit is listed twice with 2 different BV's, intro dates, tech levels, and C-bill costs. The units themselves are completely different but use the same designation.
Spider SDR-7K: This unit is listed twice and both are identical except for the intro year, C-bill cost, BV, and the 3132 version has 1 more point of armor on the center torso rear than the 3067 version.
Spider SDR-7K2: This unit is listed twice and both are identical except for the intro year, C-bill cost, BV, and the 3132 version has 1 more point of armor on the center torso and 1 more jump movement point than the 3067 version.
Sokuryou SKU-198 SurveyMech: This unit is listed twice and both appear to be identical.
Medium
Enforcer III ENF-6T: This unit is listed twice. Both versions have the same intro date. The only difference seems to be that one of them has +4 armor on the right and left leg with increased BV and C-bill cost.
Kyudo KY2-D-01: This unit is listed twice and both appear to be identical.
Heavy
Barghest BGS-3T: This unit is listed twice and both versions appear to be identical.
Lancelot LNC25-05: This unit is listed twice. One has 11 heat sinks w/ 2 lg. lasers, 4 MG's, and 1 PPC. The other has 10 heat sinks w/ 2 lg. lasers, 6 MG's, and 1 PPC.
Assault
Cyclops CP-10-HQ: This unit is listed twice. The 3025 version has extra LRM 10 ammo. The 3003 version is tech level 4, has 1 less LRM 10 ammo, and a collapsible command module.
Inner Sphere Vehicles
Light
Harasser Missile Platform Leaping Lisa: There are two versions of this unit which appear to be identical in all ways except tech level.
Saladin Assault Hover Tank (no model): There are two versions of this unit one has a standard engine and one has an ICE engine.
Medium
Drillson Heavy Hover Tank (Streak): There are two versions of this unit-one has extra SRM 2 ammo.
Assault
Ontos Heavy Tank (3053 upgrade): This unit is listed twice but they are completely different.