Welcome sam. Sounds like a far out, groovy bus dude. Ken kesey eat your heart out. I know the distributor stabbing procedure has been documented before in this forum, but in looking briefly through both this and the gas engine tech section, I did not see it stickied, so I'll go ahead and run through it for ya.
First oddity you need to be aware of in dealing with IH v8 engines is that the ignition timing is done off the #8 cylinder, not the #1 cylinder as in many other makes. As you face the engine from the front, your right hand bank are the odd cylinders and the evens are on your left, with #8 being the rear-most hole. You want to ensure that #8 is at top dead center on the compression stroke. Now hopefully the little brass bushing that the distributor drive gear rides on did not come out partially with the distributor and then fall down into where it's not supposed to go. This is a critical item so you should shine a light down in the hole and try to verify that the bushing is still in place. After that, you can go ahead and stab the distributor. Position it so the vacuum advance can is oriented roughly between 4 and 5 o'clock as you look at it from the passenger side. You want enough clearance between it and the water pump housing that you can rotate the distributor counter-clockwise a smidge to advance the timing as needed. Now, you should have all your plug wires unplugged from the cap. Remove the cap and make note of which hole location the rotor is pointing at as you loosely set the cap back in place being sure that it is properly aligned with the distributor body. That hole location is #8 and will likely be at roughly 1 o'clock, again looking from the passenger side. Connect the proper plug wire to that spot. Then it is just a simple matter of routing the remaining plug wires one at a time in a clockwise fashion from there according to the IH firing order which is cast into the intake manifold very close to the t-stat housing. Your last wire connected will be #1 as it occupies the position just ccw from #8 and begins the firing order. Don't be surprised or discouraged if you find that you have to go through this procedure more than once to get it right. It is very easy to stab the distributor off by a tooth in one direction or another, even for an experienced stabber. If the engine just doesn't quite want to start and no amount of rotation will quite get you over the hump, that means you probably miss-stabbed by just a little bit. You can either relocate all the plug wires over one position, but that requires knowing which direction to go! Or, you can re-stab the distributor one tooth in the opposite direction of whichever rotational direction was getting you the closest to lighting off, thereby increasing the amount of available rotation in that direction. Kinda 6 of one, a half-dozen of the other I guess. These engines really do want to start even when things aren't quite dialed in. You have to be fairly far off to not even get an occasional sputter. Clear as mud right? Hope that helps.
I don't think it was installed correctly in the first place or I would just put it back in the way it was. I would prefer to do it correctly and would appreciate some guidance.
