The 409, 454, and 235 6 were all about the same weight, the 283 about 100 lbs less. The cast iron T10 may be the same weight as the auto you had in there. I have 6004's in my 62 with a 409 4 speed, uncut it looks like this:
I haven't done anything to the rear, original springs and bushings, new shocks. I like the higher front end, it is higher than Dan's. The car had no hood at the time of this picture.
Welcome to the site, nice car and build. Just a word of caution, if you are using the original steering column, the 62 clutch pedal is the only one that will fit.
Don