'84 454, oil in coolant????

[Robert1970C20rstbukt]

Today I was checking the truck and it was low on oil, took about two quarts to get it in the operating range which is very odd. Normally it will use a half quart between oil changes, mostly from leaking valve covers I'm sure lol. Checked power steering, brake fluid, then found nasty brown liquid in the overflow. Pulled the radiator cap off and it had the same stuff in it, thick, light brown, and smells like oil. Pulled the radiator drain plug and it had clean coolant in bottom, let it drain about a gallon and it was still clean. I drove it to my parents house a few miles and checked the oil again, still full and clean with no coolant contamination. My Dad and I rebuilt this engine almost five years ago and it's been running great, has about 45K on it since the rebuild. Had the heads redone by a machine shop, they said they were in good condition and they did a valve job on them and resurfaced them. We checked block and it was good as well. I've ran it all these years, never had any issues. It never overheated, never used oil or coolant. My Dad's not sure what it could be either, any help would be great. I plan on doing a compression test tomorrow, and possibly renting a combustion leak tester from Oreilly's also before I tear into it.