For those that are interested, here's a quick comparison of the various LSx PCM's.

97/98 PCM
These run a Motorola 68332 Micro and also have some Delphi custom support I.C's. Interestingly they use some I.C's that were used in the old 16bit PCM's (P4, P66 etc). So this is like a hybrid between the old 16bit PCM and the current LS1 PCM's.
Flash capacity is 4Mbit (512K) but is arranged very differently to the current LS1 PCM's.
VIEW OF 1997/98 PCM CASE


VIEW OF 1997/98 PCM PCB #1


VIEW OF 1997/98 PCM PCB #2



1999+ PCM
The update to the 97/98's. Again running a 32bit Motorola Micro but this one is a custom version of the 683xx series designed for/by Delphi.
All the supprt I.C's are also custom Delphi units, from what I've found they have dedicated I.C's to monitor knock, control spark, monitor I/O pins, O2 sensor processing, and another for Injection.
Flash capacity is 4Mbit (512K).
PCM HDW numbers are either 16220610 (1999-2000) or 09386530 (2001+).
VIEW OF 1999+ PCM CASE


VIEW OF 1999+ PCM PCB



2003+ PCM
Seems to have yet another updated Microprocessor and a few other parts are added but is very similar to the 1999+ PCM.
Flash capacity is 8Mbit (1Mb).
From the outside it looks the same as the 1999+ PCM except instead of a Red connector it is Green.
PCM HDW numbers could be one of the following -
12570558, 12580786, 12583659, 12583660, 12589161 or 12589162.
Some of these PCM's are not interchangable between vehicle applications.
VIEW OF 2003+ PCM PCB



2005 LS2 ECM
Now, arrives the LS2 ECM, known as the E40.
Another upgraded CPU, but this controller no longer does the transmission control, so it is a true 'ECM'.
VIEW OF LS2 ECM


VIEW INSIDE THE LS2 ECM