Hi all Maybe I think I was smart by finding this, maybe I'm way late.
In my research into using an Adafruit compatible 320 x 240 tft (for Uno) on a Mega the most common thing I saw was using SoftSPI to access to the SD card.
Technician by trade, so never happy with a software solution if a physical one is possible.
If you look at the unoccupied P2 connector on the tft board you will see 4 tracks leading directly to the SD card holder, and 2min with a multimeter tells that the SPI interface is duplicated on the board.
Can't give pin numbers on the tft board as they have no marking but they at very close to pins 50-53 as needed by a Mega.
Works sweet.