I have 99 Suburban. Check your ground straps. In addition to the battery ground connection, there's one on the thermostat housing, one on the passenger side head facing the firewall and one underneath the alternator on the front of the engine. There may be others, but those are the ones I remember. Check them even if you didn't remove them.
If the battery tests good and the grounds are good, but still problems, I'd replace the battery cables. Originals are 26 years old. They can corrode inside the insulation where you can't see it. They may look fine, but they may not be good.
The distributor pic provided is correct. The flat side of the distributor is almost in line with the backside of the upper intake manifold. The rotor points to an 8 stamped into that little tab in the pic. It should look exactly like the pic when you have it installed correctly. Make sure it seats completely before you tighten. Your timing is set by the computer. No need to move the distributor. Set it to the 8 and you're done.
Lastly, check all the wire connections. There are many unplugged to do intake gaskets. It is easy to miss one or not get one plugged firmly together. I've done it. Then, some sensor isn't working and you get OBDII codes, etc. if you missed one.
Hope it helps.