Remote diagnoses are always risky. When you examine the circumstances you describe, the only recent variable is higher air temp, assuming you've been at present altitude for some time and your driving habits and fuel usage have not changed.
The heat soak you describe is common and can have different causes, some or all of which need to be examined separately. Trying simple fixes first makes sense, such as examining the fuel line completely on its route to the carbs. Are you sure it's not touching a hot manifold or other heat source? Correct timing and carb tuning can also affect heat soak. Some guys swear by the decklid standoff approach, either using a tennis ball as prop or decklid standoff bracket.
If you do an incremental approach, you need to keep records. You can get inexpensive remote and/or laser thermometers/heat sensors that will tell you air temp in the engine compartment as well as temp of the block, heads, etc. I suggest you start by taking temps at various locations prior to trying to fix the problem. Then you have a starting point. Take a drive, park in your driveway/garage, wait ten minutes, take temps. Then start with easy fixes first, such as decklid standoff. Drive, take temps, compare. Keep doing that until you see definite results. It's important that conditions are comparable for comparison purposes: time of day, air temp, length and route of drive, etc.
There are LOTS of threads online describing your circumstances exactly. Samba has some relevant threads that are recent and on point. When you discover the fix or fixes, please let everyone know, as that's how we all learn. Best of luck as you move forward.