An aluminum flywheel generally is not recommended for street driven cars because of the issue of it not storing adequate energy for easy start-up from a stop for most vehicle applications. You're likely to end-up having to slip the clutch for starting up from a stop light even on a level surface. Something like a T-bucket roadster, I suspect, would not have a problem with a y-block in it having a light weight flywheel..
To compensate for the lack of stored energy needed to easily move a heavier vehicle (full-size car, station wagon, truck) from a stopped position, you could give thought to changing the ratios in your standard transmission, and / or changing your rear end gears, and perhaps changing rear tire size to dial things in.
A five speed transmission like a T-5 (many 1st gear ratios possible) or a 4 speed with the appropriate 1st gear ratio would make a big difference for stop and go city driving using an aluminum (11 lbs.?) flywheel. Changing the rear gear ratio could be a big game changer for starting up from a stop with the aluminum flywheel.
My recollection with the B-W T-85 3 speed transmissions is that there are few options in cluster gear ratios. A T-85 with the R-11 overdrive can make the use of the necessary 4.11:1 or 4.27:1 rear end gears work adequately for overall drive-ability. I think that Carl in Ohio recently indicated that he has a 4.27 rear end assembly available. I've gotten a number of parts from Carl and always found him great to work with.
An aluminum flywheel should certainly help with your vehicle's ability to accelerate more quickly once it's moving! Hope some of these thoughts help you!
a.k.a. Charlie Brown
near Syracuse, New York