If you keep the '89 running you will have a known running vehicle to hook up your MS to and try tuning with - just unhook the reference timing connector so the dist. stays at base timing. Maybe set the base timing at 15* BTDC (use your timing light and turn the dist. just like any other non-efi motor) - remember to set it back when you want to control the timing using the GM ECM.
This way you only have the fuel tune up to do.
51 GMC 4.2 turbo Can't solved today's problems using the same technology/thinking that created them
