Sounds like a cool build ! Kudos for rebuilding & modifying a 4 door :glasses7:
I see 2 *potential problems* with your proposed mod's :
1.) I've heard that 340 manifolds won't fit in '63-'66 A bodies ; use the original 273 manifolds , port-matched .
2.) The A-500 ( et seq. ) won't fit without major mod's to the trans tunnel . Even a 727 won't fit without modifying the tunnel !
'63-'66 A bodies weren't -originally- designed for V8's . The 273 was a relatively tight-fit ( witness the steering box clearance casting on the left side of the 273 blocks ) ; and the 904-LA was designed for the slim trans tunnels of the early A's .
I'm definitely not trying to discourage you nor bust your chops . Matter of fact , I hope that my info is incorrect ! I've read numerous articles pertaining to 340 / 360 swaps into early A's , and they all sang the same refrain : exhaust limitations and 904 automatic restrictions .
I'll be following your progress :thumblef: :happy1:
