Hi - I had a Lazair I that became a "Taylaz" after rebuild, part of which was to convert the 185's to drive a Rotax Type A gearbox using a machined adaptor plate & cranshaft drive adaptor.
The Type A g/boxes were somewhat discredited from some early failures, using them with R503's but work fine with the much lower powered R185's. That meant they were easily available at low cost at the time of rebuild, about 1990 or so. They drive light wooden props approx 54" dia. with the R185's ported with tuned under-slung expansion chambers. I have proof loaded them on my (modified) wing to 4g limit with no discernible distortion or even movement - except in the engine mounts. My only problem was hand starting them - a bit of a pain. Sold the a/c to someone who has just left it standing in its trailer, near Toronto. Aahh well.
This is just to let y'all know what's possible - should get the same thrust as from a direct drive JPX 425.
Cheers - Alan T.