all of the obd1 code readers regaurdless of if it's a laptop, or hand held device, are cash-grabs;
All they do is give you the exact same information as the blinking codes.
I believe that the codes blink three times, and move to the next, but it's been a while since I have monkey'ed with this stuff;
IIRC the first code should be a flash, pause, flash-flash, with is "1"-"2" or 12;
This is a self check, verifying that the ECM/wiring is ok, then after code 12, it sequences through the codes, till it comes back to 12.
If you are able to get a Tech1 with appropriate modules, or another tool which gives live data, those can be worth your time and money, but if you're thinking of getting just ha code scanner of some sort I'd suggest you save your money;
Think of it this way:
When these were new vehicles, not all dealerships were setup with a Tech1, or if they had one (or two), a technician might have had to wait in line to get access to it - so the blinking codes were used by the technicians to service your car - and if they could do it, why can't you (or I)?
I am surprise that initial mechanical timing is set to zero degrees.
But having never previously worked on one of these trucks, that could very well be the case.