5.9, max safe compression?

Running the OP's numbers on 62 cc heads, .022" pistons below deck, 11 cc dish, and .028" head gasket, SCR/DCR is 9.9/7.9. 64 degree intake closure angle for the OP's cam at 106.

Point of reference, my son's recent 340 is set up to 10.0/8.2 (a step smaller cam; intake closure angle = 61*) and has AL heads and quench. So pretty safe. Spins street tires at just over 1/2 throttle with 3.55 gears, 15 degrees initial, 2200 stall.

And I have run 10.3 SCR and DCR up into the low 8's on iron heads WITH quench (60 degree intake closure angle). I had to always run premium AND I could not get too carried away with ignition mechanical advance. Good and torquey but not quite the same tire spinner as above with a 3.08 rear and stock TC. (Ford)

Edit to add: All the DCR numbers above are at sea level so actual will be a bit lower at 1000' altitude.