Thanks guys, I appreciate the responses. However, those of you saying if the .45 was a .44 magnum they'd take that, I'd suggest you look at some of the Ruger only loads in the reloading manuals or the ammo offered from Grizzley, Buffalo Bore or Cor-Bon (which are all fine in a Marlin). I've also never even seen a baloon head case, modern .45 Colt brass has no such issue and I've never had an issue with ejection or split cases.
For lights, I have seen clamps you could put on the magazine tube, so you could light it all up pretty well. Not a bad idea, and I've got a TLR-1 I can slip on it before the trip. (This would look a lot better on the 336SS than the octagonal barreled 1894!)
As far as capacity goes, I'm not too concerned. If it can't be done with 7 shots of .30-30 and 6 rounds of .357 or .45 Colt, then I did something wrong. 4 more shots in the mag of the 1894 won't help me too much more. I do usually carry a box of ammo with me if it's a long trip.