Just picked up a 69 Cuda...
You dont want to flip the 340 if its #s matching....just bench store the block and heads and save the extra grand yu need.
Gen 3 will bolt straight up to your 727 with the flex plate and bellhousing shim from MP.
If you run a kickdwn there'll be some extra $$ required with EFI.
Make sure your trans is healthy to take the xtra tq of the Hemi.