I believe that you can use ANY 1990-1997 Accord or 1992-1995 Prelude manual transmission. Generally speaking, though, the Prelude transmissions are going to have shorter gearing than the Accord transmissions, though. However, taller gearing does not always translate to better fuel economy. On the other hand, the manual Accord transmissions are quite common and easy to find. You can probably pick one up for a song at a Pick-A-Part type junkyard. Just keep in mind that you will also need the clutch, flywheel, pedal cluster, master cylinder, hydraulic lines, etc. But it is DEFINITELY doable. You will also need to get a manual transmission ECU so that you won't have issues with the ECU. It will just plug in, though.
As for the mileage you will see, this is hard to say. Generally speaking NO Accord is going to get 35-37MPG. At least not if you drive it like everybody else. However, a manual transmission swap can DEFINITELY make the car more enjoyable to drive. And on Hondas, swapping to a manual transmission will DEFINITELY wake the car up quite a bit - you will notice a decent increase in pep. So even if you don't end up reaching your mileage goal, swapping to a manual transmission is not without its benefits.
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