Frying the brain trying to figure it out

All right here's the deal. I bought an '82 528E. Now supposedly the engine has been replaced with either a recently rebuilt or an engine from an '84. Well it wouldn't start at first. It would turn over and was making an electrical sounding ticking but not starting. No spark at the wires/distributor. I figured it was the ECU due to the act that the previous owner told me that he was 95% sure of it. Well I took the battery out and removed teh computers that I found. I took what I believe was the ECU apart to look for a burn mark. None present so I put it back together and looked at the other computer. It looks like they didn't inted for ANYONE to open that other one without destroying it so I left it be and put both back into the car reconnected the computers and teh battery. I attempted then to start the car again and all I get is a rotary switch acting REALLY funny. The switch I have NO idea what it is for it resides next to the shifter and it has 3 selections. R E and 321. I unplugged that switch and got to noise but when I plugged it back in the switch clicked when I changed selections but the I'm guessing transmission warning light comes on. When I tried to start it again the switch made the noise again and went to center position and again won't stay in any other selection than the E. Anyone able to help me here? I'm busting my head over this one and can't figure it out at all.

Trouble starting... have you checked the starter?

You kind of lost me after you said you checked the computer...