Yes, they have; there were ~10 in the last auction.
the cam changes between industrial, NA truck and Turbo truck use but I recall them as being generally interchangeable, the injector pumps change as well but are interchangeable
everything else interchanges but they have different part numbers and in the break down book they look different and with some companies going to a numbers only picture free reference system for older parts because the parts numbers are different they will tell you they wont fit
There are some accessories that bolt onto the block that will not fit but not because it wont fit to the block, theres just not room for them in the configuration thats in the engine bay.
one caveat
I've been told there is a year break which as I recall is prior to the county getting the suzi and theres something about the liners and cam which make them non interchangable from early to late. I've never had personal experience of it as I've never had to do work on an engine that predates the alledged change period.
Id suggest you're about on the money with the knock being the gudgeon but ID be prepared to find that it could also be the piston side of the gudgeon combined with some piston slap.
Big ends being worn can be both your low pressure and noise problem, I'm doing this job in mine right now.
Drop the sump off and have a look.
if you're sneaky you measure the float with a DTI.
if your not you just drop a big end and shell clean up the bearing and then redo the plastigauging.
If they're bad enough to drop your oil pressure you'll see the wear easily, I can't believe mine wasn't knocking loudly when I saw the condition of the big ends. The main bearings were quite good still, oil pump had a few scores in the base plate which I polished out and one oil squirter check valve had a broken spring.
Eric