A Technodrive transmission uses a cone clutch, unlike the Hurth or ZF transmissions multi disc clutches. So it is a simplier device.

You need to make sure that the rotation matches the Perkins and your hand of the prop.

I'm not sure you can't get a rebuilt transmission with a warranty. I had my transmission replaced (after we caught a floating lobster line a couple of years ago.) I got a rebuilt transmission from Mack Boring with a warranty -- and it actually cost about the same as the labor and time of having it rebuilt locally.