I don't really want to pick on you, but when you move from trying to coble something together something from the junk you have laying around, to selling parts to someone else you open yourself up for examination.
The only reason why you might need an intercooler at 5 psi boost is you air temps are super heated by the wrong size turbo. The fact that the motor is tired (likely a little oil fouling) and your air temps are high means that your already close to detonating a 9 to 1 compression motor at 5 psi. The fact that your AFR is pig rich at 10-11 AFR is probably saving you. I doubt you will gain much power by an intercooler or a leaner AFR. Considering your exhaust backpressure is likely over 10 psi it gets really hard to make HP, the biggest cork in your system right now is the less than 1" diameter hole in the hot side of that turbo your supporting.
I am not against making crap work, years ago my first turbo project was a stock 5.0L that we stuck 2 2.3L turbos on and hacked up an intercooler off a kenworth. It was all hacked up piping, hardware store crap boost plumbing and flipped headers etc. But that motor made over 400hp at 10 psi boost, up from a stock baseline of 225. It came on boost quick and would break the radials loose at 60 MPH. There was not much money at all in that job, but it made power because it had the right parts in the right spot. It was a rusted old 81 mustang and it ran fast enough to get in trouble for no roll bar (11.50).
You don't have to listen to me or others who have already told you your turbo is to small, but don't tell someone else that they should make the same mistake. Your flange choice on your hotside kit is suggesting that.