I’m so sorry to hear about your brother. I’m sure he would be honored that you are doing this.

I don’t thing there is any magic formulation that preserves a vehicle. Synthetic was originally developed for extreme cold weather to not gell. It does have the benefit of being more slippery and can handle higher temperatures. The best thing is to change fluids regularly and check them often. One thing that gets ignored is the antifreeze. It has anti corrosion additives that break down over time. This is more critical in aluminum motors which you have. Also check your battery often. Any acid leak will cause damage. You could use a sealed battery that is unlikely to leak.

If you really want it to last, park it in a garage when not in use and avoid salted roads.