What way would you go? I like the idea of the '65 because I could keep my converter and install would be pretty easy. Im unsure whether it would blow up. The 4L80 seems to be quite a bit more expensive and difficult and Id need a new converter. Id also need a file from a truck with an 80'.
Im hoping to be very near 700rwhp with this project. Im staying with a big centrifugal blower, bigger built motor, bigger cam, maybe heads, and a little nitrous when no one is looking.
I drive the truck very carefully and rarely beat on it. It probobly wont see a track more than once or twice,

 

My tranny is built nearly identical to the flp-5 and I love it. With your application though, it may be border line. 700rwhp on a hoe would put some bind on the tranny. I think you can buy replacement 1st and 2nd tranny gears for the 80 that bring the gear ratio a little closer to the 60-65. That's what i'd do if I ever have to put an 80.

 

Im curious if I can get away with it. The 80' would have to be totally farmed out as I dont have the tools or a lift which would be absolutely neccesary. Im not to thrilled with the idea that Id have to drop another $900 or so on a new PI converter either.

 

Also would you guys recommend going with one from car-parts.com or getting a built one? Im looking to save a little money somewhere! I figure I could save at least $1K by getting a low mile on from car-parts.com. This will be going behind a forged 364, T trim, something like a 218/224, and a little nitrous.