I would not leave a trickle charger on that long un-attented... too much risk for fire/melting wires/etc.

If you don't want to jack it up, drive it up on foam blocks (the pink ones used for wall insulation). That will avoid flat-spotting the tires.

I might think about a car cover as well, depending on where the truck is stored.

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2002 X5 4.6is - Titanium Silver / Black Alcantara - Dinan Stage 2 - Bilstein/Eibach - Brembo BBK ----SOLD---
1993 318i - Brilliantrot / Tan - bone stock daily driver