How much initial timing is too much? Running hot on the highway.

Late model 440, older MP .484 cam. New Champion 26" radiator, 185 thermostat and dual 12" fans on a therm switch (on at 195, off at 180, I believe)

Now that's it finally gotten really hot here in Texas (we're in to multiple days over 100, yesterday it was 104), the Scamp is running hot after a drive on the highway. Around town, she'll get up to 195-200 and stay, but on the highway, she'll climb to 210-215 pretty quickly. Decided to check the timing finally, so I got out the old light, and it was dead. Damn, only got 30 years out of that old Craftsman. Couldn't locate a new bulb, so I bought a new light (Actron digital monster with tons of buttons). After finally figuring this thing out, I plug it up, pull the vacuum line off the can, and fire up the car. After pressing the advance button to get the mark back to zero, I look at the number on the screen and to my surprise, it reads 23.2. Assuming the marks on the car are correct, that seems a bit excessive for initial timing. Again, assuming the marks are correct, I adjusted initial back to about 12.5 and the car sounds a whole lot better. Idles better, seems to have a little more pep in her step at lower speeds too. Stayed about the same as far as temp around town, but I didn't get her on the highway yet.

So, does 12-14 sound about right for this combination? If not, where do y'all think she needs to be?