Yes, both devices are in 40-DIP packages. As I recall, the former is the industrial temperature grade version, while the latter is commercial.

I am almost certain that you are not going to find a local supply of these chips. Even the big distributors do not seem to stock much from this family (i.e., DS89C4x0-xxx). Unfortunately, your best bet is probably going to be to get these from Maxim/Dallas Direct, which typically means your parts will be coming from overseas and are likely to take at least a week to arrive, assuming they're in stock. The real problem though is that stock on these parts seems to be pretty spotty. One day they are in, and the next day they have 10+ week leadtimes, even in prototyping quantities. So, when you need these devices, plan ahead.

If this is your first DS89C4x0 project, you should really take a few minutes to familiarize yourself with the errata. Although I like these devices, some have non-trivial issues at their current revision levels. The latest revisions of the newer parts (DS89C430/440/450) seem to generally have less issues than the older DS89C420 parts, so you might want to look into them too. Pricing and feature sets of the newer devices are not too much different; all of the new ones include IAP functionality though, and offer a variety of flash sizes (16, 32, and 64 KB on the '430, '440, and '450 respectively).

--Sasha Jevtic