I have a new ZPAP92 that I want to Form 1 and add an underfolding stock. I was able to source a complete Yugo UF assembly finally.
Since the importers mark is located where the underfolder cut needs to be, I would have to buy a new receiver correct? Doing a internet search I couldn’t find a concrete answer one way or the other.
Back in the day, Nodak Spud was the best option but I’ve read that the Creative Blanks receivers are the best option today. Does anyone have any thoughts on these?

The only makings you can't touch are the serial number. If you don't touch that then cut away. But yes, Recreator makes the best blanks that are most correct for each model that they offer.

For Form 1 items you have to engrave your name (or trust name), city, and state, as you are 'making' a SBR 'somewhere' on the receiver where.  The S/N needs to be the same (I believe), but can be re-engraved elsewhere as well, since your modification would destroy the original engraving.

Call the BATFE and get clarification.  No, they are not going to come and shoot your dog.

Actually..my experience has been different... I ordered 1 Creative blank and 1 Childers blank for a long delayed M72b1 RPK build...

The Creative blank was so hard that it was impossible to drill any holes without carbide reamers (I had carbide drill bits, reamers and other carbide stuff to start the project... the Childers blank drilled easily with their supplied drill bits...(I think they are carbide as well...). The short story is that the Childer's blank fit WAY better than the Creative blank... Both the rear and the front trunnions fit way better on the Childer's blank. If I used the creative blank, I would have had to use the carbide reamers as the blank was too hard to drill with anything else...

That brings up a second question... What is the recommended hardness of a Ak receiver (regardless of type)... I know it has been posted in the past, but, going by the creative blank hardness (maybe 65 to 70 RHS, due to how hard it was to drill it) the Childers was definitely better in terms of fitment and ease of drilling...

Your thoughts are appreciated and welcome!!

Recreator is what you seek but that won’t be a standard blank and it won’t be your normal Yugo blank either if it’s a flat trunnion gun.   Either way you can go the 80% and engrave the kit serial number on it to match.  Then all you need is your info somewhere on the receiver at that point for the F1.  You can mark it all on the underside in front of the mag well.  

A lot of peeps put good stock in Childers but I’ve got blanks from recreator, AKB, Childers, AOA, and the Childers ones are down there with the AOA Polish one on my thoughts on lining them up.   I haven’t bought one in a while but I thought the Childers at some point were Polish blanks with markings and selector stops added.