how would the cmi big tube elbow headers be with the 741 cam, and would i have alot of modifications to make them work om my 32 active thunder.

My experience is that the length of the tubes in a NA application is more important the exit diameter. E-tops w/ big elbow & 1 7/8" ID tubes vs 1 7/8"ID Sport Tubes...Sport Tubes +15 HP. If I remember correctly, stock E-tops w/ 3.5" exit ID vs. E-tops w/ 4.5" exit ID was only about +5 HP.
Ben

Ben is correct. Thats why the 525 and larger came with Sport Tubes...

Whats the HP of the engine?

Never get carried away on an N/A engine of moderate size and compression with big exhaust tubes, bigger is usually not better, I think the Sport tube will make more horsepower and torque in your application than an oversize tube pair of E-Top Big Tubes that are made for blower motors. Even standard E-Tops would be better than big tube E-Tops.

Best Regards,
Ray @ Raylar