Question

I have a 98 chevy s 10 with a 4.3 V-6 that I had put a short block in it and it was running fine. I took it for a drive and it died out. It will start sometimes but it runs really rough and then dies and other times it will just crank as if it wants to start but dosent. I have checked fuel pressure it's at 60 psi and holding I have replaced plugs,dist,dist cap,rotor, wires are still fairly new I cheked engine compression it's at 135 psi per cylinder,replced ECM yes I had it programed the following parts were replaced with the short block swap oil sender,knock sensor,map sensor,TPS sensor. I checked and secured all grounds I have omh mass air flow,crank shaft sensor and Ing coil all omh ok I have hooked up a snap on scan tool vehicle has no codes. I am going to replace the fuel pump out of disstress if this dosent work my next guess would be the fuel injector fuel meter any ideas would help.

Thank You
R.Pena