First - have you seen/played a machine fully equipped with LED's? If not, go online and watch a few videos, or better yet, view one in person. LED's are not for everyone, and they often look much worse than the standard bulbs. Read up on how LED's behave; they look quite a bit different - the "temperature" of the light is often different, although newer LED's come in "warmer" shades.
The main thing to notice is that when used with feature lamps, you'll see flickering from the LED's when active, due to the nature of how lamps are activated in a pinball. Feature lamps (such as the ones that come on to count up bonus) are strobed - they are turned on/off very, very quickly. With a standard bulb, this isn't noticeable, but with LED's, this flickering is often quite noticeable.
With older Bally/Stern games, you can purchase an aftermarket lamp driver board to avoid the flickering, but I'm not aware of such an option for Gorgar.
http://www.marcospecialties.com/product.asp?ic=ULTLDB
If you only want to use them in behind the backglass, or for GI (general illumination) bulbs, not as big of a deal.
There are also newer varieties with reduced flickering that may work better for you - example:
http://www.pinballcenter.eu/english/product-informations/noflix-advantages/pinball-led-noflix.html
I'd suggest ordering 5 or 10 of these, putting them in an area, turn out the lights, and see what you think before going all out and ordering 100+ LED's.
To answer your question - for the flashers (#89), flasher versions of the LED's are available as well; you wouldn't just stick the #44 equivalent LED's in those areas.
Personally - I've seen a few games where they look ok - and many where they look really, really bad, and really detract from the game. Think before you leap.