The A5000 would basically be a Macrosystem DraCo 060 with the Alpha coprocessor slot modified for an x86 board.
The A1600 would be An A1200 motherboard with an EC 060 and 16MB fastmem built-in (if you want more, use a trapdoor expansion), it should also have a RTC and a 1MB flash kickstart with an atapi cdrom boot option. The IDE interface should be fully buffered and 40 pins, not 44. The case is modified in a way that it could hold a cdrom with some kind of metal cradle as an optional.
Built in 23 RGB to 15 pin VGA adapter and graffity card functionality (chunky modes).
