Ever heard of a hole closing up with wear? I have a 1918 block that my new .436 lifters won't fit into. The old lifters measured .432-.433 with wear showing. I have no way to measure the guides, but they are obviously smaller than the .437 shown in the MTFCA Engine book. Time to borrow a reamer I guess.
Holes don't close up with wear. I suspect the holes in your block are the proper size and the lifters are oversize.
I am not very concerned about wear in the pushrod (lifter) bores except on an open valve (1911 or earlier) engine. If the face of the original lifters is not scuffed I would use them.
It is not uncommon to ocassionly find engines with undersize lifters. I found this in a 17 block and others on the forum have reported the same. The true reason for this is unknown but one theory is that rather than scrap misground lifters Ford would save them and once in a while make a block to use them.
I was just kidding about getting smaller with wear.
I think I must have what Jim is talking about. They are certainly smaller than what the book lists as standard.
When I rebuilt my 1926 engine, it was all original including standard pistons, valves and lifters. The engine showed very little use and was not worn out. I ordered standard adjustable lifters and they measured .436. I went to install and they were too big. I measured the original lifters and they were .416. I had to drill and ream the block to fit the new lifters. I was just as surprised as you that standard replacements would not fit. As Jim stated people have come across this occasionally and there is really no known answer as to why.