[88Stanger]

Welcome! My fair sir, you are in a very good position. You have a great starting point on the "66 and now you have some possible swap parts in the square body. The place you are at is a very fun but can be very difficult also. What to do with the truck, how far to take it, how much work you want to do, how much you want to pay to have done, yada yada..
My suggestion is to first and foremost figure out what you want, what type of truck do you want, stock, mild build, crazy build, hot rod, drag, road race, I mean the list can get real long here, so figure out what you want. Note that whatever choice you make, there are consequences, how much time and effort do you want to put into it and then the big question, how much $$$$ do you want to spend?!?! The last one is typically the killer. I have completed a 1969 C10 LS Swap, it was done from the ground up with only very moderate upgrades and DAMN I spent some $$ on it. Then I go get a small back window factory short bed, no motor, tranny or bed. YA, it is nothing even near stock, not even close (to me) and I am only at the Frame completed part, and talk about $$$$!! It is DBL what the 1969 totaled out to! BUT the 1966 is going to be MY truck, in and out, all me, everything I want!
I only tell you this because on the 1969 I thought I knew what I what I wanted, but more importantly I went with what I could afford then, and well now I can afford a bit more.
So Figure out what you want in the end, but also understand what it will take, time and $$ wise and go for it!!!
This site is the best damn place for help!!!! Great Great help here!!!