There is NO problem connecting to an OBD1 vehicle if you have the appropriate scan tool or scan tool simulator, suitable software and connector cables.
ABSOLUTELY.
A listing of what is available on an '88 K1500 is at this web-page. You're looking for Post 14 and 15, but read the entire thread...it's kind of a giggle.
Unfortunately, the photos seem to have gone missing, and the photos were the best part of those posts. [Edit] Got into those two posts, fixed the pictures. They should show up now. [/Edit]
www.automotiveforums.com/vbulletin/showthread.php?t=1146067
94 k2500 no low end power and horrible fuel mileage C/K
www.automotiveforums.com
I should re-post all that on this web site with photos and all, maybe even update it with photos of the Solus Pro I'm using now. But not today, and maybe not this week. I gotta get some other stuff accomplished.
Any decent scan tool will show EVERY sensor reading, and all the computer outputs. Graphing the sensor voltages is a BIG plus, and most scan tools should do that--older ones may not. Bi-directional control--using the scan tool to change the operation of the computer is another big plus. For example, I could command the computer to switch the AIR diverter valve from exhaust manifold to air cleaner proving that the diverter valve and all the associated wiring still worked.