Sources for pre-09 5.7 long blocks / cores?

Well, a bit of an update. Just got my latest oil report back and it's not all doom and gloom anymore. Numbers dropped quite a bit, so looking like the engine is healthier than I originally thought. I think part of my issue is that I don't actually have a good idea how many miles I have on it since I first put it in the car. My odometer has basically been non-functional since I did my transmission swap, which is the same time I put the fuel injection on it. It never ran that well with a carb, so that means that most of its early life since the rebuild I have no real records of mileage. I know I've changed the oil on it a few times, but it was driven far more randomly in the past when it wasn't my main transportation. I did the swap something like 13 years ago and made a random guess that the car had somewhere between 20-25k miles on it since then. I know I've done one longer trip with it and some commuting to my old job, so ~2000 miles a year seemed reasonable. The first report I got on it though still made it sound like it was full of break in material, which seems odd given that I know I've changed the oil on it a couple of times before then at least. Maybe just all the sitting around was hard on it and drafting it back into regular service knocked some stuff loose.

Either way, definitely some more peace of mind driving it around now. It runs great, so I had a feeling it couldn't be all bad. Will have to see what the next report says, but for the time being I think I'm in the clear. Trying out the new orifice PVC fitting as well to see if that helps any of the oil consumption issues, so fingers crossed.