I don't have both side by side but I've used both manifolds and I believe the Indy 2-D is fractionally lower than the Edelbrock Performer RPM on a 440. Much bigger internally but lower at the carb flange.

Someone I'm sure has the dimensions but I'm 99% sure I'm correct, I can run a 5/8" spacer on the Indy and still close the hood of a 70 Charger, can't with an RPM