Try this thread
http://www.network54.com/Hide/Forum/...geid=991172010
it has references to other drill bit test threads, but since you alreay sonic checked it, you could probably just post those numbers and the guru's there could tell you how much boring/HP before you blow out a cylinder.
The 352 is on almost all FE blocks, from the 352 to the 427, so it is basically only identifying it as an FE. The only reliable numbers are really on the crank itself. It should be a 1U or 1UA or 1UB (there may be others) to indicate the proper stroke for a 428.
Woods428 is right, block casting numbers basiclly only tell you that it is an FE, not much else.
I am only an rookie at this, but these things I am sure of, I would leave the rest to the FE forum.
tj61@juno.com