Will a h23 fit in a 1995 Honda civc?

Yes...to simply answer the question, it will indeed fit.It will require a little work though. It is beyond the scope of this "wiki answer" format to completely answer your question, but I'll give you a basic breakdown. Option 1: This option would be to swap an entire Hseries setup into the Civic. You would essentially source an Hseries tranny from a Prelude. Get a clutch and flywheel for the setup, along with all the associated bolt ons (alternator, intake mani, exhaust mani, etc). You'd then source an aftermarket mount kit from companies like Hasport or Enjo, which adapts the Hseries setup to the civic mounting system. That's the easy part. The harder part is, that the Hseries trannies use a cable shift linkage and your Civic uses a solid linkage. You must adapt to the cable linkage, so you need a shifter assembly from an Accord or Prelude. You must then remove your entire shifter from the Civic, cut a hole to mount the Accord assembly, then cut a hole for the cables to leave the interior, and head into the engine bay. You also then need to address axles. The easy combo is to use an intermediate shaft from an Accord and use 90-93 Integra axles. From there you'll take your STOCK civic harness and adapt it to the motor. Some lengthening will be required here and there, but an H23 is pretty straightforward. The only main issues will be adding knock sensor. From there you can run the setup with a chipped Civic ecu and use Civic style saturated injectors, or you can install a resistor box and run the H23 injectors. Option 2: This option requires you to buy a Bisimoto H2D kit. This will solve several issues, but also create some. The issues it solves is it eliminates the need for an Hseries tranny, and doing all the mods to mount shifter cables, and the Accord shifter assembly. What this kit does is basically allows your stock civic Dseries tranny bolt up to the H23. Your setup is then mounted with the stock Civic tranny mountings, but a custom made driver side mount. This also allows you to run your stock axles, which eliminates the binding issues experienced with an Hseries swapped Civic. The issues the kit DOES create though are all fitment related. Your gonna need to research what's required with the Bisimoto kit. It's not too complicated...people including myself have posted pictures and how to's on Honda-tech.com. H2D kits and H2B kits are being heavily favored though, due to the inherent weak nature of Hseries synchro's, as well as the weight savings you experience. In my opinion full Hswaps are a thing of the past for the mostpart....H2D and H2B's are the way to go in most scenariOS.