[joedoh]

like mongo said, I usually hang the engine in the framerails, either from above with a cherry picker or from below with a couple floor jacks (the ones that dont leak down haha) I like to go 1 inch to the passenger side for steering clearance and keep the oil pan a little higher than the lowest crossmember. I install the engine mounts first keeping the 3 degree down (easier with jacks but be careful not to knock it off) then the trans mount.

if you are asking WHERE in the frame should you set up the motor, mock up is the best way to find out. put the cab on, motor in the framerails on the picker or the jacks and move it around. if you dont have the cab on yet, put it on for this. dont forget the distributor because its the furthest/tallest aft mounted piece that will hit the firewall. if you dont have a distributor, the passenger side head is usually the next furthest/tallest piece. if you cant get it high enough you may need a trans tunnel. if you cant get it back far enough for the fan or accessories you may need to tub the firewall.