Why 300 lbs? The ballast alone would disqualify any already-built car.
As to your question: my guess (can't be scientific) is that this would put the E36s at the back of the pack (where the E30s are). Maybe add 1.5-2 seconds? Both acceleration and handling would suffer a lot. At Road America it might be 3-4s?
As to adding this much weight, the rules would have to be revised to allow more than 200 lbs of lead. My car weighs 2850 with a passenger seat, full tank of gas (start of the race) and my large but. I don't think I could add that many interior trim pieces to make it up.
The BMW issue is really different (and goes to the politics of the organizers of BMW CR, and protecting their cars--oh maybe this is the same issue as in IT?). Classes were revised up to give/maintain advantages to certain cars.
In revising the CR classes, the breaks were arbitrary (according to the ratios-some are big, others small)...so they made sure the E30M3 was at the very top of J class (J-14.2 lb/hp) and that the E30 325 was at the top of K class (K at 16.7 lb/hp).
I class is tiny (12.5-13.9) to ensure the E30M3 stays in J, which they stretched (14.0-16.6) to ensure the E36-325 now fell into the range, but excluded everything BUT E30-325s(ask yourself why ".6" and not ".5"?). K class then reverts back to a tighter range (16.7-18.9).
On the weights BMWCCA chose to use, they are also the arbitrary #s BMW used, which vary every year (representing an "average" model w/ bundled accesories). Obviously, over time the weight of accessories/stuff (such as sound insulation) has increased dramatically...which should be excluded in comparing cars at "race" weight.
Dan
[This message has been edited by m3ltw (edited February 25, 2003).]