I strongly recommend to switch OFF chipcache. Your card should show up as 56MHz if that's what it actually is. Try cleaning the connector, and re-check that it really provides the computation power that you expect from the 56MHz card. If in doubt, post a Sysinfo screenshot.
Size of the ACA620 and ACA1220/ACA1232 is the same as the prototypes. Only the colour is different, and some things have been added. The ACA620 is the first one to come out of production sometime next week. I have added a freezer framework to the memory controller and also found a way to make almost all of the 16MByte physical memory available to special software: After running ACAtune with the "maxmem" option, you have a total of 11.3MByte Fastmem, a fast kickstart "maprom" of up to 1.5MByte, 1060KBytes of freezer memory and about 2.5MByte for special software (hoping to find someone who writes a RAD: -like driver for that).
On the mechanical side, the mass-produced ACA620 got a ventilation hole for the 68EC020 processor.
During development of the ACA620, I found a way to optimize cache for the 68020 processor, and changed something in the circuit of the ACA1220 that lets me put that optimization into ACA1220 as well. I have also added a level-7 Interrupt connector, but can't tell (yet) if the freezer-functionality will fit the logic. That's the kind of changes that you can expect - no change in board size ;-)