At 440" and a .557 the 1 3/4" will be fine but IMO it's important to remember the collector size will tend to limit the RPM that peak torque will be produced, so if the collector is too small for the compression and cam it will lower the HP trajectory (rate of HP rise per 100 rpm) beyond the peak torque RPM.

It's pretty easy to adapt and weld a larger slip on collector (such as the ones sold by Shoenfeld) to inexpensive headers, Generally, a 3 1/2" collector will likely pick up your HP compared to a 3" even with the same primary tube sizes, all else being equal. That is provided/assuming you will also have a low restriction system downstream of it.

ET improvements can be found when the converter, cam and collector size are optimally tuned for one another.