<VV> Differences bwtween 1964 and late cylinders

[Bill Meglen]

After several frustrating tear downs and reassembly a friend who is building
a 140 engine utilizing a late case It has been discovered that rebuild parts
were ordered believing the engine case was a 1964 110 Powerglide.  Despite
careful repeated measuring and plastigauging at each assembly a knock
difficult to isolate, but sounding like piston developed soon after run in.
If has been since learned that the case was from a 1967 PG 110 rather than a
1964.  In reviewing the Clark catalog it appears that 1964 pistons are
unique to that year.  Cranks, cams, rods, pistons, bearings fit 1960-1969.
Can anyone tell me what is unique about 1964 barrels and what are the likely
consequences of their being assembled in a late case (with 140 heads)?

Bill
Gardnerville, NV