I'd guess 250 lb or there about for the little Clark 5 speeds.
As Ed says don't may much for it, or any more than scrap for a direct drive. They're difficult to get parts for. If it's in good shape no reason not to run it. If it comes to rebuilding one you're probably better off looking for a whole decent one instead.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-