Need a temporary motor and good 340 block

Move on to another block. Not cost effective to fix that at that price.

One of those 360's will do. Early, late with roller cam, or Magnum. Pick you poison.

Even thought 360 are externally balanced, the Scat cast or forged crank stroker kits can be bought with internal balance. All that would allow is for your old vibration dampener and torque converter to be re-used. Those are the only two things effected by internal vs. external balancing.

I all ready have a rotating assm. for a 340 block, I didn't think to check the lifter bores. I've never seen a bad lifter bore on any engine I've worked on, if it wasn't for bad luck I wouldn't have any luck at all.