Hey. I'm new here but I wanted to put SR20VE too in my Nissan March a few years ago. I even prepared and bought some parts like a manual transmission kit from Pulsar VZR. It has LSD. Then I gave up. The mechanical part isn't so difficult as electrical. Our cars have CAN bus. SR engine-powered cars were older so you can't easily connect the wire.
The coolest SR20VE in K12 I found is this:
I remember I saw some info about this build here too but I wrote letters to the owner. They are professional race car builders, they know stuff and they couldn't connect the original dashboard. Original electrical power steering.. they couldn't use it too and replaced it with a hydraulic one. It's running on the racing ECU with nitro and it's freaking fast. I'd say it's a budget of a couple of such cars.
Of course, it can be done cheaper but if you want to keep things close to the original, working dashboard, A/C, it may require MUCH professional electrician job and time.
I saw a couple of SR16VE builds in Japan but none of them was "clean" or daily driver. And I talked to a Japanese man who drove one of these cars. He said it was fast but unbalanced. SR engine is old and heavy. For this weight, you can get VQ engine.
I'd prefer to stay with CR/HR engines OR go with MR. At least there's a chance to use OEM parts and get a close-to-original balanced build.