408 Magnum stroker running hot.

Ok I get you
This is an easy fix .
Set your timing thus, just do it, and we can argue about it at another time.
Set your power- timing (no V-can) to 33*lol
Set your idle-timing to whatever.
Make sure the centrifugal does not start until~200rpm higher than idlespeed.
Make sure the all-in does not occur until after 3200/3400. If you have to modify or swap your springs, get it done.
Put a vacuum gauge on the sparkport, there should not be any vacuum there at idle. Rev it up to 2000rpm; now there should be some vacuum. Close to what is in the intake.
If you have vacuum at the sparkport at idle, see note-1
Now some math; with 3.73s and 27s, 55mph=2550@zero-slip. If your tach reads higher, make a note of it, and you can calculate your slip from it.
Knowing your minimum cruise rpm is 2550@55;
hook up your timing lite, and measure your centrifugal timing at 2550 or thereabouts.
Hook up the V-can to the SPARKPORT, and repeat; what is your cruise timing at ~2550 with the Vcan hooked up?
Inside the Vcan up in the nipple, is an allen headed socket screw adjuster. I think it's a 5/32. Loosen off by turning it CW I think. Do not force it . When it gets tighter, stop!
Now repeat the test at 2550. If you got more timing Good, that is the max you can get with this Vcan. If you didn't get 56* yurscrewed.
Ok no! just kidding, 56* is just the target.
With the timing spec I gave you,I would expect 29* at 2550 plus the V-can, which can vary from 9 to 20 depending on the model you have. Lets say yours has a typical 13, so the total is 29+13=42@2550rpm with full vacuum to the can.
Roadtest time!
Is it better? If timing was your problem as I am inclined to believe, then it should be better. But if the V-can is giving you detonation, see note-2.
Now; for testing purposes only: Rev it up to 2550 and crank the timing with Vcan to 50degrees, then roadtest it. You will have to go easy on the gas-pedal to prevent detonation. Take your timing lite along. After a successful run; stop the car, pull the idle-timing back to 16*, turn around and go home; Which was better?
If 50* was better, we need to go there ,at least, permanently. To do that, you will need to pull the V-can off, chuck it in a vise, and file the stops shorter, we'll talk about that later.
But first, we gotta revisit your power timing.
Perhaps you already know what your power-timing can be without detonation.In post #1 you said 16/33 but did nor hint at the rpms. So if you get the 33* after 3200, then you are already golden.
Back to the Vcan. Measure the length of your stops, and make a note of it together with the amount of vacuum advance this produced. If this was less than 15*, the then file off ~3/32. Make a note of the new stop length. Put it all back together and fire it up. Run it up and figure out the new amount of vacuum advance, and write it down on the paper. Calculate the amount of advance for whatever you took off, and convert it to degrees per 1/16. We might need that later.
Ok Rev it up and set the cruise-timing to 54* at 2550, then Idle it down and make a note of your idle-timing.
and ........ you guessed it; it's roadtest time again And again,get it up to cruising speed easy, listening for detonation.
If it's better, and your idle timing was more than 16*, then we will have to shorten the stops some more. If your idle-timing was say 20*, then we need 4* more from of the Vcan. So pull it out and with the previous calculation you made, file off whatever you need to to get the 4*, then put all back together. This time, disconnect the Vcan and set your power-timing to 33*, hook up the Vcan, and roadtest again. This time your power timing is back to normal so you can smash the gas,lol.
Was it better, and is it GOOD now.
We are now on the final leg so this is important to know.
That's enough for today.
Oh wait!
If you still have overheating problems, all is not lost, you now have the basics of getting about as good a fuel-mileage as is possible with that cam.
I'll be waiting to see how this turns out.


Note-1
This indicates that the primary throttles are too far open, and will have to be addressed.Make sure your PCV is hooked up and working. IDK how to make the required changes with your Sniper.
But You will need to find an alternate source of bypass air. I'm assuming you have a functioning PCV plumbed. If you have an IAC then crank it up and close the throttle, until the vacuum drops to zero at the sparkport. If you don't do this, or something like this, you could very well have detonation. Do what you gotta to make it happen.

Note-2
You will have to slow the Vcan down. First, check you total-timing with the Vcan at 3500. Then stick your allen wrench in the nipple and crank that screw all the way to the other end, IDK maybe 6 or 7 turns. Then recheck your total-timing with Vcan at 3500 again. If it changed; then put a turn or two back in and check it again. What you want this to do is slow the vcan down. But if you turn it too far, it will start subtracting Vcan timing. When you find the sweetspot, roadtest it.

Note-3
If you cannot run Vcan timing without detonation, on the best gas, then your engine has a problem, and We'll have to figure it out.