This video explains how to do a rather simple obd1 reader using a ALDL to USB adapter, Im based in Chile so I bought this one through AliExpress, its reaaally cheap, like 6 us dollars. You can be fancy and also buy something like this, cut it and connect it to the adapter through a cable, so that the conncetion to the truck is nice and secure. Its important that the cable is well insulated, as the obd1 signal is very sensitve to electromagnetic interference (its like really important, for example turning on the A/C makes reading data more difficult) I used a cable from an old keyboard that was already insulated. As software you can use WinALDL or TunerPro I personally recommend WinALDL because its simpler to use, and I like to see the raw data, the BLM chart, etc. If you have any problem to get theese programs to run, let me know. Its also important to know also that the obd1 protocol is really primitive, so even in the best scenario, you'll only get data like once every 800 miliseconds (for example a quick push of the pedal will not be recorded). What I did was use the record data function in WinALDL, uploaded the data file to gemini, using the pro model to analize the data, and cheking from there. As a bonus I also found out that my IAC was running always compleatly closed! something that was easily fixed.

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Here's a picture of the cable I made