Sorry I missed you message and was not intentionally ignoring you. No 4.10 is not to low, nor is a 4.56, but that's getting there. In 3rd gear 1.00 I'd hit 3,000RPM at 68MPH with a 4.10, with a 4.56 I'd hit 3,000RPM at 60MPH. My typical cruise speed on the highway with my trailer is 60-65, but sometimes I'm forced to go a little fast due to traffic patterns. I don't want to cruise much higher than 3K on the highway, but we all know a small block can run around 3K all day long with no issues. 70's Class C RV's on the chevy chassis rolled with 4.10's and the TH400, Dodge ran the 727 again most had 4.10's. Both my 4.10 RV's had no problem running 65MPH. Plus my truck has the 700R4 so when I'm not towing I can run in overdrive. Which by the way with the 4.10, in overdrive would make 70, 2,100RPM and 80, 2,400RPM so neither are to low with overdrive. I've got a ton of hills here and mountain passes to go over going from 3.41 to 3.73 would not be enough. Now if I was running a 454