[bhazard]

Interesting hybrid swap, kinda the opposite as my b6t festiva, though many similarities.

The donor car for the b6t festiva swap (merc capri or mazda 323gt) is the same width as a festiva, so the axles are the correct length.
You also drop the whole b6t engine harness into the festiva, all the plugs for the engine are there, and goes straight to the ecu. You then run a few wires to ignition switch for the hot connections.

My best yet is 38.8 mpg, .3 better than the best I got in the donor car, and about 10 mpg lower than what I averaged in the stock festiva (lol). Still got some issues, like an exhaust manifold crack thats drawing in fresh air over the o2 sensor causing it to run rich. Im running o2-less for now. More engine and bigger tires, but its lowered a bit and I swapped a taller 5th gear in. Im hoping to maintain at least 40 mpg out of it in the end, and I expect a much bigger number out of this CRX.