Rear end gearing

Here's another good RPM calculator to play around with, it's been real accurate with all my cars.

Simple RPM Calculator | RANDYS Worldwide

With your 4.10 gear, 27.8 tire, and 113 mph trap speed you should be around 5800 RPM.
After you get your converter built correctly you should trap at a higher mph and probably around 6000 rpm. I would keep the 4.10 gear with that cam and tire.

My 8" ATI converter slipped less than 3%.