Maybe we should do a test of a bunch of different Corn COB LED bulbs, and see how they do.

I wouldn't use a high-powered (>10w) LED lamp in any small enclosed fixture, especially outside where it will sometimes be much warmer than room temperature. A high-wattage CFL would be better but probably would have a reduced lifespan also. 100w MV would likely work well if you can find the right ballast (and a place to put it). It might also be possible to stick a pair of 13w preheat PL lamps in there with the chokes mounted inside the fixture itself, if you can find room and are willing to modify the fixture pretty significantly.

Why not replace the glass with something clearer?

Now there's an idea...it just involves finding the right glass and cutting it to size.

Or, you know, find a different fixture.

If I were you I would get a 100w merc postline ballast (some members here have them and would be willing to part with them) and use that instead.

A 20 watt CFL won't provide nearly enough lumens, and besides it gets cold here. I did order a 35 watt LED. If it breaks after a short time I may have to go to a different fixture.

You'll have to keep us updated. I'm curious to see how well it holds up. By the way, I'm guessing that LED will only draw about 20 watts. Pretty much any eBay-grade LED product won't be nearly as powerful as it claims to be (though there are exceptions). Also, if it has a plastic cover, I'd actually suggest removing it to help with heat dissipation (though make sure no one tries to touch the lamp with power applied).

So the answer is "They really are that bad"
Top one was sold as 800 lumens. It uses 4.7 watts and I measured 24 foot candles (as opposed to 37 from an incandescent 60 watt)
Bottom one was sold as "35 watts". It uses 2.8 watts and puts out 18 foot candles.

Obviously completely unacceptable for my fixture. So I'm at loss if I can use it. A CFL is out of the question because of the cold, and there's no place to put gear for HID. (Although I think White SON would look nice I'm in the US). Clear glass doesn't fit with the style of my house and 100 mercury is too much wattage, not much of an improvement over the 100 incandescent there now.

Lower wattage Mercury with remote gear. Or if using CFL, change between lower power and higher power CFLs for the hot and cold parts of the year respectively (taking advantage of the enclosed luminaire in the cold times)

The distribution from a corn is different than from real Incandesncent, so it matters from which direction you measure the illuminance for each lamp. But still, with 4.7W input power you'd be lucky to get 360Lm (the Ebay LEDs are not top efficacy, so below 80 Lm/W), obviously not 800 Lm