I've owned and swapped five s13s with sr20s. All parts I replaced was on all of them:
thermostat
Coolant hoses that runs into the firewall
top and bottom radiator hose
belts
spark plugs
Obviously you want to change engine/transmission oil
Never had a problem. All had compression of around 155-156 psi on all 4 cylinders. I bought my sr swaps from reputable and no name shops, all are the same. I usually just have them do a leak down test before bringing it home and look for signs of fluid leaks. I usually bought the swaps that have been unwashed because you can see if they were previously leaking before or not.
Also if you're not planning to upgrade the turbo anytime soon, take off the stock rubber intake and spin that turbo. I made the mistake of not checking the turbo on one of my engines one time, got home and the compressor would not budge. I had a spare t25 so no biggie.
If injectors are bad, just buy some z32 injectors...they're also purple top 370cc injectors just like the s13 sr. If upgrading anyway, Deatschwerk injectors are very reasonably priced and comes with flow sheets.