Every engine family has its limitations and unique features. If you are a bracket racer that needs 600(?) Hp or less, it is pretty hard to come up with a motor that can make close to that power with stock block, heads, valvetrain,etc. Sure there are expenses that you won't have with a bb, but for the size of an engine you can build with those stock parts and a stroker assembly, you would be in a Gen III fairly reasonably.
An early 5.7 with 390 to 400 cubes, stock heads that flow what, at least 300cfm as is? Any body built a combo like this with high compression and as big a cam as the stock rockers and lifters will handle?
Even if the power per$ was the same with a bb, you still shave 100+ pounds off the front end!
Obviously at some point the old wedge would pass a Gen III in hp per$ at some point, but I would think it would be. Fairly high point for budget racers.