In my quest to convert my DAK P220 to a DA/SA I need to isolate the incompatible parts so I dont accidentally mix them up. And sooner or later, I would.

Which parts do I need to put aside?

I converted a DAK 220 to DA/SA this past fall.
TopGunSupply has a pretty accurate listing (https://www.topgunsupply.com/faq.html) of the conversion parts needed. I also found that MidwestGunworks' parts diagrams and parts listings to be very helpful in checking for DA/SA vs DAK parts / numbers. That said, I still had some guessing involved. For example, it seems that the DAK's sear is identical to the non-SRT sear (SEAR-2) for the DA/SA model. But, I'm not sure of that assumption and TGS had included the sear as an incremental part needed for conversion. (Ultimately, I was installing SRT parts as I did the conversion, and thus did not have to confirm that assumption.)

Of the items listed by TGS, the only exceptions that I noted:
The Hammer Strut Pin is now typically already installed in the newly-purchased hammer.
My DAK 220 (a police trade-in) came with DA/SA poly grips. I'm not sure if Sig even produced DAK poly grips.

The Top Gun Supply FAQ list is accurate and complete, except that it is not necessary to change the sear when converting from DAK to DA/SA. Old DA/SA sears cannot be used in DAK mechanisms because they lack the cutout (circled below) that permits the sear to be pivoted sufficiently far during the trigger press.

DAK guns, however, necessarily must have the modified sear, otherwise they wouldn’t work. The cutout does not affect their use in DA/SA guns, and therefore they can be used in DA/SA guns, and in fact later DA/SA SIGs had sears with the cut.

Thanks; that helps. The sear I pulled from the DAK 220 liked identical to the original sear that I replaced in a 226 classic carry. Both were produced within the last 4-5 years.