Yes, I am very familiar with the 454/7.4 liter. You must remove the distributor cap there is no other way to get this thing timed if you've had the distributor out. Don't worry about tampering. Its a 98, the warranty ran out a long time ago and you can do whatever you want with it!!!
get that cap off so you can see the rotor. You will need to know what post on the cap is for the #1 cylinder. If you don't I'll send you a pic. If you do, great! Sometimes its even marked on the cap.
The only way to tell if it's actually on the compression stroke is to remove the number 1 spark plug
. It's the first one on the driver side. place a finger over the spark plug hole. Now rotate the engine BY HAND until you feel air start to push against your finger. When you feel this air continue to roll the engine over until the mark on the crank pulley is at the 0 mark on the timing indicator. Now you are at TCD #1. that's where we want to be. Now, you will notice the electrical connector on the side of the distributor. That needs to point in the directon of the driver seat so the wires will reach it. temporarily install the cap back on the distributor. locate the #1 post and follow it down to the base of the distributor and make a mark on the distributor itself so you will know where #1 is with the cap off. install the distributor with the electrical connector facing the driver seat and the rotor pointing at the mark you just made (#1 on the cap). If the rotor dosen't point to #1 with the distributor FULLY SEATED, then pull it out and move it tooth in whatever direction it needs to go and stick it back in. Make sure it fully seats when you put it back in. Sometimes the oil pump drives will give you a bad time getting it in, but just keep wiggeling it and it usually goes in......
Keep in mind that if it's just barely off, you can rotate the distributor a little one way or the other, just don't go to far or the wires to the back of it won't reach or will be pulled too tight. snug your hold down bolt and put your wires and everything else back on. Now here is the fun part
While the truck should run, it still isn't timed properly. The only way to do this is with a scan tool. You must read what's called the cam offset on the scanner. it's basically a timing reading. adjust the distributor until it reads 0 plus or minus 2. Keep in mind it' wont update until you rev the engine over 1500 RPM so make an adjustment and rev the engine before going to look at the cam offset again.
This should get you going! you will have to pull that cap off to get this right.