chuck plissken,
the handi rifle will handle the ruger #1 loads stated above (it is also chambered for the s&w 500 cartridge (a 60,000 psi round)). so, i would use (and do use in my buffalo classic) the data behind door number three!
my load uses a 460 gn lead cast performance bullet. it chronys at a little over 1800 fps (that's out of a 32" barrel mind you). can't find the load info, but the lyman manual has load info for a 475 grain lead gas check bullet. that should get you started. as always, start low and work up.
luck,
murf