While I haven't played Silver Bayonet, you could probably just ignore the supernatural side and just use it rather than adding another ruleset.
There's a few people who are doing a similar thing with Frostgrave as a more general medieval skirmish...and they did have a couple games of Stargrave for a modern one (Not sure if they're doing more as they shifted to gaming on a different night...swapping with a GorkaMorka campaign that's been ongoing for a long while)