I have a brand new 3.8 #25500012 block, 3.545 bore, 2-bolt front and rear mains , 4 bolt center mains, 3 front caps are steel- rear is cast, has the oil pump pickup boss. as nice as it gets!! $3200.00 mike
I have seen this a number of times, block is basically cast to be used at 3.800 bore but some odd rules or class breaks might warrant the use of say a 3.600 bore , so some blosks were cast with extremely heavy cylinder walls (small bore size) to accomodate this I have had 4.1 blocks with 3.700 bores!! hope this helps mike