Knobguy

I am new to the Mercedes world. I recently purchased a1992 MB 310 otherwise known as a T1. It does not have the original motor in it. I’m told the engine in it is from a 1984 190E. It’s a carburated 2.3 L, M 102 motor with unknown milage. I can not get #3 and #4 cylinders to fire. I checked compression and all cylinders are consistently 148-150 PSI. I changed out the spark plugs, then the cap and rotor, then the plug wires, then the coil, then the distributor, all to no affect. Any advice on where I should go next would be greatly appreciated. Thanks