63whoopie,
Just some food for thought...
I too have a '63 C-10 (LWB Fleet not short step) and I, like you, wanted to get away from the high rpms. I swapped a bone yard T-5 into my truck behind a 230. My original tranny was a 4 speed so I didn't have to worry about changing from the column shift, but that isn't a real big deal anyway. The bolt pattern on the T-5 and your current tranny should be the same so you can use your current bell housing and clutch set up (no adapter plate needed). There will likely be a difference in length in the two which will require that you drive shaft be cut down, but you can usually find someone to do that for ~ $100. If you just call a bone yard and ask for a T-5 you'll likely get a response somewhere in the $400 - $500 range...tell them BS that you can get one for $100 on eBay...that made my local bone yard guy change his tune ASAP. I paid $150 for the T-5 from a truck that I watched them drive into the yard. I drove it around a little to make sure the tranny was OK and then they removed it and loaded it into my truck.
I can now cruise at 70 mph down the highway and the truck isn't under any strain at all. My truck had a 3.73 ratio rearend and the T-5 worked out perfectly. I am now in the process of building a 350 so I can swap out the 230 and I'll still be running the T-5. There are a bunch of T-5 posts on this site...search for them and you'll get a bunch of info and links about how to plan it and do it. The install ain't that hard as long as you pay attention to what you're doing and ask questions here if you don't know something.
