If you found sludge ANYwhere in that newly built/fresh engine, it was NOT tanked long enough. You done right to pull it down, now get it tanked AFTER you pull ALL the freeze plugs and threaded oil galley plugs you can find. Take note where you removed the oil plugs so that you don't forget to replace all of them ! You also might want to have the block magnifluxed for cracks. When you get it all assembled it'd pay BIGtime to do your initial fireup on a run-in stand instead of in the car.