Spark Knock after engine swap

Hey folks, I recently swapped out the 5.9 in our 1995 Ram 4x4 for one out of a 1998. After a fiasco with flex plates and torque converters not making nice that since been resolved, now it wants to detonate above 3500 rpm under WOT. I swapped the plugs for some Autolite 3923's gapped at .040 but that didn't help. I have yet to run some 93 through it to see if that helps as the tank is full of 87. I just recently discovered it was doing this as I hadn't really romped on it since the swap. And I'm used to pulling some timing via a twist of the distributor but i dont thin it works that way on these trucks. Only other issue is surging while cold, but after it warms up it runs great. I'm wondering about the lack of an EGR on the new motor. I used the factory 1995 computer and harness, but the 98 motor didn't have an EGR. I had to reuse many of the sensors off the 95 motor because the ones on the 98 were different. Any ideas to combat the pre ignition? Thanks, you guys are awesome.

I would swap the 95 exhaust and intake manifolds over and run the egr like it was intended. During this I would go ahead and make sure the plenum fix has been done and that none of your plug wires are crossing.

Do not twist the distributor. Distributor doesn't control timing on these trucks. All spark advance and retard is done via the PCM. Distributor is aligned so as fuel injectors fire at the correct time.

^ Agreed. Something is making it run hotter chamber temps.

I may resort to the intake swap after the 93 octane trial. I did fix the plenum gasket while the new engine was on the stand with one of those Hughes kits, and peering down the TB it's bone dry in there. I also swapped on some Pacesetter headers while it was out. They have a provision for the EGR tube but I just made a block-off plate for it.

Alright guys, on the way home tonight I made a pseudo full throttle run and then shut it down and coasted into my driveway. I let it cool a bit and pulled all the plugs on the passenger side and they look brand new, like super white, as in lean white. I put a brand new denso fuel pump in it less than a month ago but for some reason I suspect a lean condition under throttle. Culprit(s)?