A-1 8" converter?

4800-5400 does sound a little on the loose side.

Not if that is what your engine wants. Years ago I had an old B&M 3800 that was way looser than anything I've had in the last 15 years, even though they flashed a lot more. Just because a converter will flash 5000 doesn't mean it'll slip at anything below that rpm. Plus I never had any heat issues with any of the three converters mentioned above, use a good external cooler.