Kshef,
There isn't a clear cut answer for your question. There are at least 3 versions of the 3.8 liter Stage II block. 2 have the same casting # 25500012 and are Off center. One is an On center with casting # 25500153.
There is an early off center block which is machined from the same casting as the Stage I block but has 4 bolt center main caps and 14 head bolt holes. These early blocks don't have siameese bores and are prone to cracking on the outside between the freeze plugs.
There is a later version (circa 1985) which has siameese cylinders and is much stronger but quite rare and as stated above has the same casting # to add to the confusion.
The last version is an on center block with casting # 25500153 and is an underbored 4.1 liter block. All of the above blocks will set you back between $2500 and $3K for a new one. Prices for used ones will vary greatly upon condition. Shop carefully.
Neal