a hacked together running car will cost you far more than the initial price chasing problems and replacing stuff
a car with no power train is going to cost you a few grand up front but you will at least know that the engine and work is good
both will likely need work on the brakes, suspension, bushings, general maintenance
expect either car to cost at least $6000 to get to proper running condition
$3k for a gsr with JDM front most likely has a rebuilt title. Big issue for some, nothing major to others. But $3k is cheap and sets off a red flag. If you can do the labor 100% by yourself, the shell isn't bad. I'd personally go with the one with the best body. Engines are easy to fix, paint gets expensive fast.