most all of it is custom built .you can get up to 730+cid with the 4840 bore space stuff so the 5.000 and 4.900 is far from cheap oil pump dry sump . cams .cranks.intake is custom as for bore size 4.750 can happen .so cid can be big .dart may not list a 5000 .block but will make a billet 6160 block and thats over 20.000 for just the block most of the 4.900 were short deck gm pro stock did make a iron block that may be the dart 4.900 block now