[v8volvo]

Hard to say on the question of oil in the coolant, that's always a guessing game. It can take a while to get all the oil out if it makes its way into the cooling system. When I have dealt with one of those situations after a leaking headgasket or oil cooler it's taken a few flushes over a period of multiple weeks, and sometimes I add a little bit of gentle dish soap (just regular liquid soap, not dishwasher detergent) to help break down the oil. Even after all that and multiple flushes you might still see a little residue from time to time. It's hard to get it all at once as the oil wants to cling to the inside of rubber hoses, insides of the rad and heater core, etc.

If it doesn't seem like the amount of oil is increasing, and you don't see other symptoms of headgasket trouble (loss of coolant, overheating under load, etc), then I would try another flush or two and see if you can get the oil out. But if it seems like there's more and more oil in the cooling system, or the engine is losing oil faster than usual, or any other signs of HG trouble, then you might still have more work to do.

Kudos for what you're doing, it's fun to hear about one of these engines getting used this way. Sometimes it seems as if you might have easier paths available to keep your car reliable, though, other than tearing it down time after time. Do you own the correct tools for setting camshaft and injection pump timing? As one example, if timing is too far advanced it will quickly destroy headgaskets, damage pistons, and cause other harm much like the problems you described that recently sidelined the car. These engines don't usually require as much or as frequent major internal work as you seem to have to do, particularly the bottom ends are normally extremely durable and strong, and with head studs and a healthy cooling system, HG and head trouble is also more or less avoidable. What about taking a shot at doing it slowly and by the book before your next event? Might keep the car on the track longer and be more driving and less wrenching.

If you're constrained by the budget rules of chumpcar/lemons (forget which one this is running in) for buying the expensive special tools, I'm sure folks on here would contribute to your cause by loaning what they have.