cm2350 fuel in oil

[hct5]

we installed a new short block, head, fuel pump tappets and housing on this unit around 10k miles ago and it has been running great, last week we noticed that fuel is getting into the oil somewhere. we ran the truck on a bucket full of dyed fuel and did not see any injectors leaking. the fuel return line and check valve have been replaced. what could i check next to find the issue? could the fuel pump head be leaking into the pump housing?