Awesome find! Wish I had see this earlier, I could have told u exactly what it was...
As far as the difference between Dragon's Lair, and Space Ace, there's a WORLD of difference... If that cab was infact a Space Ace, it was the conversion style... Meaning, in an original Dragon's Lair Cabinet... I built one from scratch, and am currently waiting on my artwork to arrive...
Also, here's another vote for restoration... I say do it man! And I love the way you're keeping us updated! Peeps here love pics!

If you're looking for the marquee plexi, and rails, I make reproduction parts for these cabinets... Currently I have have 1 set of rails, and 1 marquee plexi left... I also have a run of speaker grilles left... Probably 6 or 7 pairs remaining... Keep in mind, that the marquee plexi I sell, doesn't include the artwork... Just the 3 sided plexi... Get with me for pricing...
I don't know if you know it or not, but u can get reproduction scoreboard plexis at Arcade Renovations, and a working scoreboard from Quarter Arcade... I also reproduce the scoreboard cable... hehe
Any way, good luck with the restoration... I'll be watching to see how things come along!
PS ~ How's the vinyl look? Still in good shape?