swap 1996 318 EFI onto 1967 273?

I would spend the money on a tbi system from holley or whatever. The 87to 93? Tbi systems are not considered tuneable by any means.
The magnum immediately thereafter is much better, but as mentioned the transmission bellhousing has to be notched for the sensor. Manual and auto require different sensors.
Flex plate/flywheel needs to be adapted to the 904.
Engine/trans would be easier yet.