Ford V-10 6.8L Seized Lost Oil Pressure

Sorry about your engine. I had a similar incident with my old 5.4 2V engine. I wasn't anywhere near 5K RPM, maybe 3K going up a sleight grade, northbound in Seatroit's new tunnel. Fortunately in my case, I was only a few miles from home, just returning from about 3 months on the road. We coasted through the last bit of the tunnel and out to a clear striped no traffic area. I wasn't driving hard, just putting along and all of a sudden my oil pressure idiot light came on and within seconds, the engine seized. I was using WIX filters on the engine. In all my years, I've never had a FRAM go bad on me or have reason to distrust the brand, I just wanted to buy a high rated filter. On my 6.0 Liter PSD, I only run Motocraft filter and liquid products. I put in another engine from on of the reman companies and had good results until the plastic oring seal in the crossover tube broke out, blocked the heater hose which is where the water pump gets it's supply from causing a severe overheat and ruined the head gaskets resulting in ARP studs and Cometic MMX head gaskets and a bunch of performance upgrades. 

If you're still having trouble separating the flexplate, I recatt on mine, we pried the bellhousing apart from the engine enough to get a flat ratchet end wrench in there to loosen the nuts off the studs on the torque converter. It's in your interest to leave the torque converter on the pilot shaft, unless your going to replace it but it sounds like you don't need to with low miles. I installed MMR coolant adaptors on the back of the heads to provide better cooling and I understand your V10 will benefit from them more than the V8. 

I hope you get things back together and on the road again. Take care.