I think there may be some confusion here. All Amigas except the 500/600/1000 have a dedicated accelerator slot that is use to plug in an accelerator card, usually but not always with an uprated cpu already attached to it. The accelerator cpu card takes over the system cpu bus completely and the original cpu, if there is one (e.g. most A4000s have no cpu on the mainboard), remains idle. There's little use in taking a 68020/030/040 off of an old Mac unless it is to be used as a replacement for a burnt pga-style cpu on an Amiga accelerator card (or back in the day it was possible to buy an accelerator board new w/o the cpu).
The original cpu in the A500/A2000 computers is a large dip-style plastic pack 68000; not pin compatible with any other Motorola chips sans the 68010. The A2000 can be upgraded with either 1) a dedicate cpu card in the 86-pin accelerator slot or 2) by removing the 68000 from it's socket and plugging in either a 68010 or a special accelerator that plugs directly into the 68000 chip socket. Option 1) is the more common solution and option 2) is the primary (excluding the GVP530) upgrade mode for the A500.
