235 cu dizzy wobble

[yeah_yeah_na]

I have just imported a 60 longbed stepside into NZ from LA. It arrived a couple of weeks ago.
When I first started it I noticed the dizzy wobbled in the block, it runs what appears on the face of it to be a factory dizzy, I've pulled that and can't see any signs of wear, the guy I purchased the truck off tells me its a new repro 235 cu engine block. I have not run the numbers to check this out but I was wondering if anyone else has had this issue? The truck runs fine at 60mph but I do notice a little pre ignition knock at low speed, not under load, the opposite to what you'd expect . I am using the truck as everyday transport, its my only transport, so I'd like to repair it.