I've got a 429 and C-6 that i'm putting into my 66. it had the orig. 352 and 4 speed. has anyone done this in this truck? and how did it go?  

This is a very simple swap. You can use the engine and trans mounts from a later Ford that came with a 460 (same as a 429), and of course a lot of the minor parts will work as well. Gas mileage should be about the same, maybe better. Look into gearing the rearend higher, and I guarantee you will get better MPG. Is your '66 a F-100 or a F-250?  

its an f-100. i've already got 4:10 for the rear. the hardest part i'm seeing in all of this is just finding the time to get all pf this accomplished through all my deployments  

4.10:1 are deep gears. Good acceleration, and poor gas-mileage. You'll get about 10 whether the truck is loaded or empty. Yeah, I know all about finding the time. I had plans on working on a '53 F-100 I just bought, and then passed out after dinner. I could go out in the garage now, but I don't think the neighbors would dig hearing an air impact wrench at 11:30. Anyways stick to it, it will be a good swap when you get it done.