urethane over enamel


Mopar shop
I have an engine in the shop that I had painted a few years back with acrylic enamel. I recently had to put a cam in it and it has a few areas to touch up (bolt heads, chaincase cover etc.) and the valve covers need resprayed. I have small amount of paint left from the original job, but not enough to cover what I need to.

As I bought the original paint off of a restoration shop (private label) I was going to purchase another pint from them for the touch ups, but I haven't been able to reach them.

So my question is this - if I end going to my local jobber, can I just color match this in urethane and go over the enamel or am I asking for trouble ?