An 020 isn't necessary. The A500/A2000 3.1 ROM can be used with the standard 68000 CPU. Since rdhcook has an A500+, it's probably fitted with the 2.04 ROM now. There's no advantage in keeping that, so go for the 3.1 ROM! With a kickstart switch and a 1.2 or 1.3 ROM it's possible to switch between 3.1 and 1.2/1.3 to play older games, but don't bother with that unless you can get it cheap, rdhcook.
/Martin