Everyone is pretty much correct.
1.)
An RSX front clip wouldn't look good AT ALL on a ';91.
2.)
An RSX front clip wouldn't FIT a '91.
3.)
It would take a ridiculous amount of custom work that you probably don't know how to do.
4.)
The money spent on this freak of nature could BUY an RSX.
5.)
Even if you did successfully create this hybrid retard thing, that would be like ruining an RSX because you've got your crappy little Integra motor in it. A K Series motor, and the RSX front- again, you would be ruining an RSX, and you could have PAID for an RSX.
You basically want to ruin two perfectly good cars.
BAH! GO PLAY IN TRAFFIC.