Painting over restored paint job

[ItWillBeSlow]

I recently acquired a nicely restored truck bed for my project that I will be repainting to change the color. I will also be welding closed some trim holes in the bed sides (40ish).

The bed is very nicely restored and almost a shame to repaint. I'm in a bit of a rush with the weather and would prefer not to strip down the current paint job, but paint over it instead.

The current paint I beleive to be DuPont Chromabase with clear.

Can I shoot SPI epoxy over the clear? What grit do I scuff with?

Since I will be welding the trim holes shut I will have some bare metal before epoxy and I would put filler over the epoxy where the holes were. Then top coat with SPI high build, seal with SPI epoxy reduced at 25%, basecoat, clear.

Is this a good plan? I realize I do not know what's under the current paint job but that is not the purpose of this thread.