go with a double reduction with the first reduction using the smallest drive sprocket you can get that has an odd number of teeth.
this will keep the sprocket sizes down to manageable sizes and keep tooth contact within reason.
do it up in a welded steel case and add some oil, then off you go.
i have seen 350 chevy engines with dual roller cams run well over 300k miles and the chains still look pretty good.
so maybe you use a chevy cam and crank gear as the first reduction, and follow that with the needed reduction in single row #50 for the final drive?
the chevy cam drive is not running in a pool of oil, it is just what leaks out past the cam bushing and the front main brg, and is thrown around inside the case.
also if you try to do it in a single reduction, you ought to provide for some sort of auto/spring loaded tensioner, if for no other reason but to keep the chain whip under control. there will likely be issues if you don't, so plan for inclusion of some sort of tensioner before hand when it is easier to incorporate rather than later.
another viable option would be either a cog belt (probably a better solution) or a microgroove/serpentine type belt (not as good as a cog drive but better than a chaindrive in my opinion,, neither would require lube but both would benefit or require a tensioner.
fwiw
bob g