Around '84 the injector threads were changed from coarse thread to fine thread - 6.5 injectors are fine-thread, won't fit in the early heads.
6.5 injectors are higher 'pop' pressure than 6.2 injectors - the early 6.2 Inj Pump -housing and mechanicals - is not designed to provide those higher pressures.
Even the 6.5 IP soon began shredding itself to pieces - the higher pressure caused the steel cam-rollers to disintegrate, resulting in metal particles all thru the system, which then ruined the next pump when the system was not completely purged.
Big bucks, non-warranty, all at the customer's expense, IP and all.
Solution was ceramic rollers and other stuff, indicated by the "Green Tag' on the top of the pump, or the later blue Stanadyne label.
You can turn up your IP and advance the timing to compensate, but you're probably asking for quick IP failure if not a green tag blue label pump
Remember - metal particles don't travel from the tank thru your filter to the IP - metal particles travel from your failing IP to the fuel tank, then back to the filter, which then plugs up the filter.