I can think of a few reasons why lacquer 1k is a very poor choice and no reasons why it’s a good choice since it’s 2025 now and not 1985.
Hence why it is rarely used anymore and not widely available. Just like VCRs and CD players.
But
@custodian, depends what you’re gonna do with the truck. Is it going to be subject to weather? UV? Moisture? Chlorides?
If none of the above, any quality 2k DTM or DTR will provide as good of adhesion and long term protection from humidity and even direct moisture as an epoxy or acid etching primer.
There is zero reason to top coat any of the above direct to metal primers with a filler primer until you’re ready to get er done. And a couple reasons why it’s not good to. Primarily being moisture absorption.
And no primer will have great uv resistance or even good UV although epoxy is the best option if you’re gonna park it outside long term. Dunno if you’re talking a year or a decade before you paint.
If you plan on driving it, especially in the winter (Catawba, Michigan?) do yourself a favor and squirt it with some sort of paint after whatever primer you use.
Don’t worry about reducing your prep/sanding requirements in the future because that’s not a thing, no matter what you do, you’ll have lots of sanding and bodywork to do before final paint anyways.