if your installing AC then i would stay with forced air heat.
no sense installing 2 systems. $$$ mega bucks $$$
frame it and insulate it like you would a house.
a pole barn is tricky to insulate well.
also think about partitioning your shop into heated and unheated sides.
my shop is 50x50, i have a 20x30 always heated work room,
a 17x30 heat as needed car bay and the rest is unheated.
all these doors go into a 20x50 unheated space.
there is a second door throgh the 16 ft door into the heat as need space.