Re: 1962 manual. 3 speed vs 4 speed: pros/cons
 

I think you are making the correct call by keeping the 4 speed because you are gaining the granny gear and loosing nothing.

Re: 1962 manual. 3 speed vs 4 speed: pros/cons
 

It is a matter of personal preference. 2nd. and 3rd. in the 4 speed are slightly lower than 1st. and 2nd. in the 3 speed, and the reverse is lower. I find the 4 speed much nicer to drive for this reason. I use granny low to pick up hay in the summer and to feed out hay in the winter.
If you were buying a new truck back in 62 you would pay extra for the 4 speed, I think that back then the 4 speed as well as the long wide box would be one of the most coveted options.
But for a mostly city driven pickup the 3 speed would be fine, many people like the column shift tucked up out of the way.
And another thing removing a 4 speed without a transmission jack is a backbreaking job.