fiftycal, small runs of large castings can be fairly costly. Not to mention the large amounts of machining and fixturing that needs to be done to the casting. That broken down between four to five parts would not be cost effective. Now if you make about fifty, then when these shops run out of original blocks, they can buy them from you. At least the ones that aren't afraid to admit they don't have the parts will.
Seriously though, if it's going in a plane spend the 100 to 120 thousand for each overhauled engine. That money should be there if you can afford one of the planes Allisons went into. If it's going in something else then make the blocks out of solid billet, it will be cheaper.
PS, I'm very happy with the three Allisons I work with using "FAA approved parts" from certain engine builder(s). I also don't have to worry about cracked cylinder liners.
Brandon
[Edited by Scott WRG Editor]
[Edited out of curiosity]