Grinding noise only when accelerating

[Olds.PhD]

Need some help on a new transmission noise. I've had my Tremec 6-speed for a few years at this point with no issues. I recently swapped from my Olds big block to an LS. New bellhousing, new flywheel, new pilot bushing, reused the clutch (as it only had about 5000 miles on it), and reused the throwout bearing. I did check runout and it was way off - required .014" offset dowels. Got those in, rechecked and its good now (about .003 max variance on the dial). Rechecked my throwout bearing clearance, and its within the .125 to .250 gap that Silver Sport Transmissions recommended. Fluid was changed when I did the swap since I might as well.

Now, it has a horrible grinding sound only when accelerating. When backing out of the driveway, no sound. When coasting down the hill to get out of my neighborhood (up to 20-30 mph), no sound. As soon as I start applying any load, it starts grinding. At first I thought the driveshaft was grinding against something. But after the first drive I confirmed, no marks showing anything rubbing there.

Attached is a video. Also, you'll hear a ticking from the engine - haven't tracked down whether that's piston slap or a lifter. It doesn't really go away, so I'm leaning toward lifter. Pulled it out of a junkyard, so hoping driving it will pump it back up, but if not, new cam and lifters will go in. Not really as concerning as the grinding noise right now.





I'd rather not just throw parts at this. No problem replacing the clutch if that's what's wrong, but it didn't have many miles and was in good shape, so I eliminated that as an issue, but maybe I'm wrong?