Fox, I think you'll be satisfied with the four speed and 4.10 and as Jerry posted, that 261 will run all day at 3k with no problems. I've posted this a dozen times, it's not a very good video and the sound is pretty bad. But at least it does give you an idea of what it's like to ride in a stock 1950, 3600 216 equipped with it's original SM420 4-speed and a 4.10 gear from a '69 or '70 3/4-ton. The tires are Michelin LT215/85 R16 and I'll run it up to 55mph or 60mph most of the way. At 3k this will keep up with traffic on the expressway, that is, if it's not posted over 65mph. So...come take a ride around the block with me:
Denny Graham Sandwich, IL
Denny I want to compliment you and your truck - it is smooth and steers very nice.