HI Turnpike_Rat and welcome to this forum
You're right, Gauntlet Legends is one the best 'modern' arcade game cab'
Running Gauntlet Legends & Gauntlet Dark Legacy is a great idea, but you need 2 pcb, and a lot of 'Switch box', in order to swith all the wires ( video, all the joystick & button, credit, etc ... ). An easy task on paper, but a lot of patience for doing it
Are you an DIE HARD arcade collector ? If you're a purist, you probably won't to destroy your actual control panel...
So why don't you buid the top panel like I did, and build a mame/daphne/computer setup... and it that way, you'll able to play anything
For the Dragon's Lair side art repro, this is the best place to go :
http://www.arcaderenovations.com/store/home.phpGreat quality and... under OFFICIAL licence
By the way, can you post pictures of your Gaunt' cab