A friend of mine is using in 81 or 84 block and that requires different lifters he said from some other regular 351 that people use. He said he has his has both front and rear.
I guess it will depend on which block I end up using ?
Your friend is probably talking about the difference between the later roller 93+ F4TE blocks and earlier non-roller blocks. Yes, you will have to know which block you have and which lifters to run. If you want to run rollers in the earlier non-roller blocks, most people either run link bar retrofit roller lifters or a small base circle cam with the block tapped for the spider and dog bones to run rollers. I haven't looked at sourcing an OEM F4TE for years but know they used to be a little harder to come by then an earlier block...
The oil pan is a rear sump design. Like most 302/351 oil pans in a mustang, you will have a front and rear "sump" area that will need to be drained, but the pickup is in the rear.
I'm assuming you saw my answer above (before the whole fox body to sn95 discussion) to your throttle body and intake question also. Just some suggestions.