vivivivivibration

That makes a lot of sense.... hard to say what parts they used LOL. I would expect a reman place to grab any set of SBM rods and put them in.... hopefully yours were the correct later heavy rod, but who knows. Early rods 273/318 rods were bushed and about 32 grams lighter on average so they could conceivably have ended up in there with those floating pin pistons. Just no way to know all buttoned up.

The one set of reman rods I checked out had a length variation of .019" !