Sorry to step in on a thread...but the following quote hit a nerve given I have been doing some extensive reading recently for my own mod.
As you can imagine from these plain numbers USSR had no chance to stand Nazi-Germany on their own. Especially crucial was the logistical support by locomotives, fuel, rubber, medical goods, explosives, trucks and cars. Of course without the imported tanks, fighters etc. USSR would have fallen even faster.
I would question the validity of this type of view and the source in which the information was obtained. It is a recently emerging fact that with the exception of trucks and tanks (mostly in the first part of what the Russian's term the Great Patriotic War), the USSR had more than enough capacity, manpower and willpower (oppression of Stalin's regime?) to both outproduce, outnumber and grind down Germany in almost every way during the war. The military's capability was the reason for the disaster of 41 and the repeated mistakes of 42 and the first half of 43. Not its manpower or industrial capability.
Recent archival records, statistics and other sources within Russia documented by David Glantz, Walter S Dunn and Steven Zaloga (as a good starting point) clearly show this industrial and war economy advantage. The USSR was a pathetic military beast at the start of the war due to Stalin and his paranoia (purges).
However, by 1943, the USSR was well ahead compared to Germany in every way even with the loss of over 40% of their fertile land, industrial centers and population to German conquest. German industry was hindered by Hitler and his archaic system that ensured no one individual could hold more power than him. This was also evident in the German military where commanders would (more prominently in the later part of the war) be isolated from exposure of other armies and their operational objectives.
Another thing to note is that GDP is not an accurate indicator of a nation's industrial might or power during WWII. Germany's GDP would be higher than the USSR's given that its population had the means to earn and spend more during the war just like the USA and UK. The USSR's economy was purely geared to defeating Germany at any cost including working for food alone and not being able to buy any form of goods or services.
Prior to Albert Speer, Germany's industrial capacity was not even geared towards a true war mobilized economy and was still producing consumer goods (some might consider this a wastage of capacity). Contrast this with the USSR's low GDP industrial base which solely focused on winning the war.
To provide a simplistic example: Producing 500 civilian radios, 200 civilian vehicles and only 120 sophisticated PzKfw IV tanks a month does not contrast well to 1000 crude and unsafe T-34s a month.
The figures I provide are generalized, but the example highlights what I mean. German civilians got trinkets during the war, Soviet civilians got 18 hours in a factory and hopefully a large enough slice of bread a day.
I encourage you to look further into this interesting area as it really helps put this enormous struggle into perspective.
A good starting point is this useful site:
http://www.armchairgeneral.com/rkkaww2/weapons/afv_production.htm#tanks41
Whilst I hate using Wiki as a source, this page contrasts the numeric superiority the USSR had over Germany even when subtracting lend lease:
http://en.wikipedia.org/wiki/Military_production_during_World_War_II
And finally, a simplified total of Lend Lease aircraft and tanks which demonstrates the small percentage the contribution played directly on the battlefield:
http://ww2total.com/WW2/History/Production/Russia/Lend-Lease.htm
NOTE: Rubber, medicine, trucks and 'other' supplies were vital, but the USSR did adapted and improvised when confronted with shortage. Fuel was never a real issue and natural resources were in abundance in the Ural region.