I have a TACTIC 650TX & 624RX in transit to be used in a RTF electric. Are these components suitable for use in large or giant scale a/c where longer range is required?

Those components will have great range. As long as the model is in direct line of sight by the unaided eye, you'll have full control.

I have to agree with Bill, I have used my TTX650 and turned my Slow Stick into a tiny red dot in the sky with no loss of control.

i have a big stick 60 size 67" w.s. and this is not giant scale but pretty big. it is also a gasser powered by a 20 cc vvrc engine. that's valley view r/c. i fly three other nitro models also with my 650 tatic all using the 624 or single antenna rx. i admit i should have the dual antenna one in my gasser and will get one soon. but no issues so far..........love it.