Edelbrock LD4B - what's the operating range?

Very hard to give an exact rpm number because the peak airflow of any intake manifold is going to be dependant on a few factors, one of them being the cubic inches it is feeding.

The LD-4B is listed as having a 1500-5500 rpm range in my 1979 catalog. Edel says the performance will be enhanced throughout this rpm range, but is not limited by it.